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Helicases are molecular motors with many activities. They use the energy from ATP hydrolysis to unwind double‐stranded nucleic acids while translocating on the single‐stranded DNA. In addition to unwinding, many helicases are able to remove proteins from nucleic acids. Bacteriophage T4 Dda is able to displace a variety of DNA binding proteins and streptavidin bound to biotinylated oligonucleotides. We have identified a subdomain of Dda that when deleted, results in a protein variant that has nearly wild type activity for unwinding double‐stranded DNA but exhibits greatly reduced streptavidin displacement activity. Interestingly, this domain has little effect on displacement of either gp32 or BamHI bound to DNA but does affect displacement of trp repressor from DNA. With this variant, we have identified residues which enhance displacement of some proteins from DNA.

The aim of this research was to detect the skin which comes from goat and pig using PCR-RFLP method so the raw material used in rambak product was discovered. The comparison of combination between goat and pig skin was 100, 75:25, 91:9, 94:6, 97:3, and 99:1. PCR-RFLP uses the universal primary from from mitochondria cytochrome b gen which results in the length of fragment of 359 bp. The restriction enzyme used in the DNA cut is BamHI enzyme and BseDI enzyme. The result of the research showed that seven samples have been successfully isolated perfectly so the total bands of genomic DNA have been obtained which is clearly seen and amplification with target of cytochrome b gen results in PCR product of goat and pig of 359 bp. The digestion's result using BamHI enzyme gets fragment size on 359 bp in length on goat samples and length of fragment size of 359, 244, and 115 bp on samples which contain pig. The digestion results of using BseDI results in fragment size of 359 bp in length on goat samples and the fragment size of 359, 228, and 131 bp in length on samples which contain pig. The conclusion of the research is PCR-RFLP using BamHI enzyme and BseDI enzyme can be used to detect the types of pig skin, but can't be used to detect the goat skin.

Endolysins have been studied intensively as an alternative to antibiotics. In this study, endolysin derived from a phage which infects methicillin-resistant Staphylococcus aureus (MRSA) was cloned and expressed in Escherichia coli pET28a. Initially, the endolysin was cloned using BamHI/ XhoI, resulting in expression of a recombinant endolysin which was expressed in inclusion bodies. While solubilization was successful, the protein remained nonfunctional. Recloning the endolysin using NcoI/ XhoI resulted in expression of soluble and functional proteins at 18°C. The endolysin was able to form halo zones on MRSA plates and showed a reduction in turbidity of MRSA growth. Therefore, cloning strategies should be chosen carefully even in an established expression system as they could greatly affect the functionality of the expressed protein.

In this study, novel p-benzimidazole-derived calix[4]arene compounds with different structures, and a benzothiazole-derived calix[4]arene compound, were synthesized by a microwave-assisted method and their structures were determined by FTIR, 1H NMR, 13C NMR, MALDI-TOF mass spectroscopy, and elemental analysis. The effects of functional calixarenes against bacterial (pBR322 plasmid DNA) and eukaryotic DNA (calf thymus DNA = CT-DNA) were investigated. The studies with plasmid DNA have shown that compounds 6 and 10 containing methyl and benzyl groups, respectively, have DNA cleavage activity at the highest concentrations (10 000 μM). Interactions with plasmid DNA using some restriction enzymes (BamHI and HindIII) were also investigated. The binding ability of p-substituted calix[4]arene compounds towards CT-DNA was examined using UV-vis and fluorescence spectroscopy and it was determined that some compounds showed efficiency. In particular, it was observed that the functional compounds (10 and 5) containing benzyl and chloro-groups had higher activity (Kb binding constants were found to be 7.1 × 103 M−1 and 9.3 × 102 M−1 respectively) on DNA than other compounds. Competitive binding experiments using ethidium bromide also gave an idea about the binding properties. Docking studies of the synthesized compounds with DNA were performed to predict the binding modes, affinities and noncovalent interactions stabilizing the DNA–compound complexes at the molecular level. Docking results were in good agreement with the experimental findings on the DNA binding activities of compounds. Based on these results, this preliminary study could shed light on future experimental antibacterial and/or anticancer research.

The published data indicate that the bacterium Clavibacter michiganensis subsp. sepedonicus (Cms) shows a notably low degree of intraspecific variation, and most of the molecular diagnostic methods could differentiate among subspecies groups but lacked the resolution to detect genetic diversity within subspecies. The present study describes effective differentiation of 50 isolates of C. michiganensis subsp. sepedonicus by the PCR MP method using five restriction enzymes (ApaI, PstI, BamHI, XmaI, HindIII). By analysing the electrophoretic patterns obtained by the PCR MP method performed with the applied restriction enzymes, each of the 50 tested isolates could be identified and distinguished from the remaining isolates. The PCR MP method of bacterial strain identification can be used in epidemiological studies, particularly for excluding the isolates of C. michiganensis subsp. sepedonicus as a source of primary infection.

In vivo control activities test of BCA candidate is required to evaluate its effectiveness. This test involved identification of the fungal species that inhabited the experimental plant after inoculation of BCA and pathogen. Identification of inhabitant fungi in the BCA control activity test can be conducted by culturing the fungi on artificial media. Fungal species can be identified based on morphological characters or genetic characters of fungal culture. This study was conducted to determine the potential of PCR ITS-RFLP molecular markers in the initial selection process of fungal isolates before identification based on DNA sequences and to select the enzyme that produce polymorphic PCR ITS RFLP pattern. Three enzymes (DraI, EcoRI and HinfI) were successfully separated 8 fungal cultures used in this study into three groups based on the pattern of PCR ITS DNA, while five other enzymes (BamHI, BclI HaeII, HpaI, and HindIII) were failed to cut the DNA ITS fragments, except for one isolate.

It is crucial to detect multiple tumor markers (TMs) for cancer diagnosis. In the study, an endonuclease-linked multiplex immunoassay for TMs detection, with alpha-fetoprotein (AFP), carcino-embryonic antigen (CEA), carbohydrate antigen 199 (CA199) as models, was developed using microfluidic chip electrophoresis (MCE) for DNA analysis as platform. Firstly, three endonuclease (EDOs) labels were prepared by labeling secondary antibodies of TMs with EDOs (BamHI, PstI, EcoRI), respectively. Then, the primary antibodies of TMs were co-immobilized on the bottoms of 96-pore plate. Finally, the TMs and labels were simultaneously incubated in the pore to form various sandwich immunocomplexes. The EDOs on them can cut their corresponding DNA substrate strands into half fragments which can be separated and detected by MCE. The signal ratio (Ih/Is) of half fragments (Ih) and substrate (Is) was proportional to logarithm of TMs concentrations from 1 pg mL−1 to 10 ng mL−1 (U mL−1 for CA199) with detection limits of 0.35, 0.3 pg mL−1 for AFP, CEA and 0.36 U mL−1 for CA199. The multiplex immunoassay was successfully employed in human serums. More importantly, based on the signal conversion mode, MCE for DNA analysis can be easily extended to detect many diagnosis markers and has applicable value in clinics.

The temperate, generalized transducing phage ΦHD248 from Bacillus thuringiensis subsp. aizawai (H-serotype 7) was shown previously to mediate transduction within subsp. aizawai and between subsp. aizawai and subsp. kurstaki (H-serotype 3a3b). Here it was found to have a broad host range, plating on 7 out of 14 H-serotypes tested. Cotransduction analysis using ΦHD248 revealed two linkage groups in H-serotype 7 : bio-2-his-2-met-1-cit-1-arg-2-lys-3 and trp-9-purC1-thi-1. Preliminary characterization of the ΦHD248 genome revealed a linear double-stranded DNA of 47.15 kb. A restriction site map is reported including a total of 10 sites for the enzymes BamHI, BglII, SalI and SstI Enzyme SalI was found to have a unique cleavage site which if not located in an essential region could be used as a cloning site. The ΦHD248 genome was also shown to lack cohesive ends and appears to have a partial circular permutation.

Tomato leaf curl New Delhi virus (ToLCNDV), a bipartite begomovirus (genus Begomovirus, family Geminiviridae), was originally described in tomato in India in 1995 (Padidam et al. 1995). The virus apparently remained confined to the Asian continent for about 20 years and has only recently been discovered in Europe. In Italy, ToLCNDV was detected for the first time in 2015 in zucchini squash in Sicily (Panno et al. 2016) and later on in other regions of continental Italy (Panno et al. 2019). Recently, epiphytotics of ToLCNDV were reported in central and south Italy, associated with yellowing and leaf curling symptoms in pepper crops (Luigi et al. 2019). In 2016, a large-scale survey was conducted to assess the distribution and the genetic diversity of the viral isolates spreading in Italy. Samples collected at that time included cucurbits and solanaceous plants, including five leaf samples from five distinct eggplant (Solanum melongena L.) plants of cultivar Violetta di Napoli that showed yellowing and light curling of the apical leaves and noticed in a cultivation located in Campania region (Castel Volturno municipality). A few Bemisia tabaci individuals were noticed associated to the cultivation. All five leaf samples tested positive for ToLCNDV with ImmunoStrip (Agdia, Elkhart, IN). These results were confirmed by PCR using ToLCNDV-specific primers TLCNDVCP1/TLCNDVCP2 (Parrella et al. 2018) on the total DNA extracted from each sample using an E.Z.N.A. Plant DNA kit (Omega Bio-tek, Norcross, GA). Amplicons of the expected size (∼1.0 kb) were obtained only from the five symptomatic plants, and the nucleotide sequences of these isolates were identical. One representative sample (Som-166/16) was selected for full-length amplification of the genome (DNA-A and DNA-B-like sequences) using the rolling circle amplification (RCA) method with an Illustra TempliPhi amplification kit (GE Healthcare, Piscataway, NJ), in accordance with the manufacturer’s instructions. RCA products were digested with different restriction endonucleases to obtain a 2.8-kb linear DNA fragment. Among the different enzymes tested, BamHI resulted in a maximum DNA fragment length of 2.8 kb, which was cloned into a BamHI-linearized pUC19 plasmid. The ligated products were transformed into a competent DH5α strain of Escherichia coli, and the positive clones were sequenced in both orientations at Microsynth Seqlab (Gottingen, Germany). The obtained full-length DNA-A (2,738 nt; GenBank MN782303) and DNA-B (2,686 nt; GenBank MN782304) sequences showed the highest percentage of nucleotide identity with the ToLCNDV Italian isolates Caa-164/16 (GenBank MK732932) for the DNA-A (99.82%) and Cum-45/16 (GenBank MF688671) for the DNA-B (99.48%). Eggplant leaf yellowing caused by a ToLCNDV variant has been previously described in India (HQ264185 for DNA-A and HQ264186 for DNA-B) (Pratap et al. 2011), but the Italian and the Indian isolates exhibited only 90.20 and 79.00% nucleotide identity with respect to the nucleotide sequences of DNA-A and DNA-B. The Som-166/16 isolate was very similar at the molecular level to previously reported isolates from Mediterranean countries and belonged to the European strain ToLCNDV-ES, because the percentage of nucleotide identity was 98.83% for DNA-A with the ToLCNDV-ES strain A-MU.13.ME/4.3 (GenBank MH577751) and 97.88% for DNA-B with the ToLCNDV-ES strain B-AL.15.ZU/2.1 (GenBank MH577658) (Moriones et al. 2017; Panno et al. 2019). The ToLCNDV-ES strain evolved from ToLCNDV isolates of Asian origin and adapted to infect cucurbits (Moriones et al. 2017). Nevertheless, this report presents further evidence, in addition to a previous report (Luigi et al. 2019), that ToLCNDV-ES isolates can potentially pose a threat not only to cucurbits but also to solanaceous crops as well, because this is the first finding of ToLCNDV in eggplant in Italy. Control measures against ToLCNDV are limited and mainly based on vector control, cultivation in protected environments, and the prompt elimination of infected materials.

A digital detection strategy based on a portable personal glucometer (PGM) was developed for the simple, rapid, and sensitive detection of hepatitis C virus (HCV) RNA, involving the release of glucose-loaded nanoliposomes due to coupling-site-specific cleavage by the endonuclease BamHI. The glucose-loaded nanoliposomes were synthesized using a reversed-phase evaporation method and provided an amplified signal at the PGM in the presence of HCV RNA. Initially, a 21-mer oligonucleotide complementary to HCV RNA was covalently conjugated to a magnetic bead through the amino group at the 5′ end of the oligonucleotide, and then bound to a glucose-loaded liposome by typical carbodiimide coupling at its 3′ end. In the presence of the target HCV RNA, the target hybridized with the oligonucleotide to form double-stranded DNA. The symmetrical duplex sequence 5′-GGATCC-3′ between guanines was then catalytically cleaved by BamHI, which detached the glucose-loaded liposome from the magnetic bead. Following magnetic separation of the bead, the detached glucose-loaded liposome was lysed using Triton X-100 to release the glucose molecules within it, which were then detected as an amplified signal at the digital PGM. Under optimal conditions, the PGM signal increased with increasing HCV RNA, and displayed a strongly linear dependence on the level of HCV RNA for concentrations ranging from 10 pM to 1.0 μM. The detection limit (LOD) of the system was 1.9 pM. Good reproducibility and favorable specificity were achieved in the analysis of the target HCV RNA. Human serum samples containing HCV RNA were analyzed using this strategy, and the developed sensing platform was observed to yield satisfactory results based on a comparison with the corresponding results from a Cobas® Amplicor HCV Test Analyzer.

International audience; Oenophages have so far been mostly isolated from red wines under malolactic fermentation (MLF), and correspond to temperate or ex-temperate phages of Oenococcus oeni. Their genomes are clustered into 4 integrase gene sequence groups, which are also related to the chromosomal integration site. Our aims were to survey the occurrence of oenophages in a broader and more diverse collection of samples than those previously explored. Active phages were isolated from 33 out of 166 samples, which mostly originated from must and MLF. Seventy one phage lysates were produced and 30% were assigned to a novel group with unusual genomic characteristics, called unk. All unk members produced similar RAPD and DNA restriction patterns, were negative by PCR for the signature sequences previously identified in the integrase and endolysin genes of oenophages, and lacked any BamHI restriction site in their genome. The data support that development of additional and novel signature genes for assessing oenophage diversity is now required.

Background VIM-type enzyme encodes the most widely acquired metallo-β-lactamases in Gram- negative bacteria. To obtain current epidemiological data for integrons from enterobacteriae in hospital, the study characterizes the genetic structure in In1059 by comparison with In846 integrons harbouring VIM gene and other class 1 integrons including In37, In62, In843 and In1021 with the aim of identifying the putative mechanisms involved integron mobilization and infer evolution of relevant integrons. Methods Six of 69 recombinant plasmids from clinical strains were found to be class 1 integrons by digestion with BamHI, drug susceptibility testing, conjugation experiments, PCR amplification, integron cloning and sequencing, genome comparison, and detection of carbapenemase activity. Results The sequences of the six recombinant plasmids encoding In1021, In843, In846, In37, In62, and the novel In1059 integron had approximate lengths of ~4.8-, 4.1-, 5.1-, 5.3-, 5.3- and 6.6- kb, respectively. The genetic structures of these integrons were mapped and characterized, and the carbapenemase activities of their parental strains were assessed. Conclusions Our results suggest that the six variable integron structures and regular variations that exist in the gene cassettes provide a putative mechanism for the integron changes. Our study has also shown that the genetic features in the integrons named above fall within a scheme involving the stepwise and parallel evolution of class 1 integron variation likely under antibiotic selection pressure in clinical settings. Electronic supplementary material The online version of this article (doi:10.1186/s13756-017-0204-1) contains supplementary material, which is available to authorized users.

Purpose. We explored the efficiency of Rv1458c, the gene encoding a putative ABC drug transporter specific for the Mycobacterium tuberculosis complex (MTBC), as a diagnostic marker. Methodology. A 190 bp region of Rv1458c and a 300 bp region of hsp65 were targeted in a novel duplex PCR assay and the results were compared with those for PCR restriction analysis(PRA) using the restriction enzymes NruI and BamHI. Species identification of a subset of the isolates (n=50) was confirmed by sequencing. Clinical isolates of M. tuberculosis (n=426) obtained from clinically suspected patients of pulmonary tuberculosis and mycobacterial (n=13) and non-mycobacterial (n=8) reference strains were included in the study. Results. The duplex PCR assay correctly identified 320/426 isolates as MTBC and 106/426 isolates as non-tuberculous mycobacteria(NTM). The test was 100 % specific and sensitive when compared with NruI/BamHI PCR restriction analysis and highlighted the use of Rv1458c as a diagnostic marker for MTBC. Conclusion. The duplex PCR assay could be developed for use as a screening test to identify MTBC in clinical specimens in peripheral laboratories with limited resources.

Leaf curl disease with severe curling, vein darkening, and vein thickening was observed on papaya plants in a field in Qurayat district of Oman during December 2013. Disease incidence ranged from 50 to 70%, particularly in young papaya plants. The presence of a large population of whiteflies and symptoms observed on papaya plants suggested that the causal agent could be begomoviruses (family Geminiviridae) and associated satellites. Four leaf samples with mild and severe leaf curling were collected from the field. Total nucleic acid extracted from symptomatic and healthy plants using the CTAB method were used as a template to amplify circular DNAs using Φ29 DNA polymerase, and products were digested with restriction enzymes to identify fragments of 2.6 to 2.8 kb typical of geminiviruses. BamHI yielded fragments of ~2.8 and 1.4 kb when the digested products were resolved by electrophoresis on a 1% agarose gel. These fragments were cloned and sequenced using a primer walking strategy in both directions. Sequencing results confirmed the exact sizes of 1,303, 1,358, and 2,765 bp; the sequences were deposited in GenBank under the accession numbers HG969296, HG969297, and HG969260, respectively. BLAST results showed that the first two sequences are Tomato leaf curl betasatellite (ToLCB; isolates Pap-2 and Pap-3) showing 97% sequence identity with a previously reported ToLCB sequence (Accession No. KF229728). Both satellites encode a single gene in the complementary sense strand referred to as βC1, which showed 97% sequence identity to ToLCB (HE800551). The viral sequence (isolate Pap-6) showed four genes in the complementary sense (the replication-associated protein [Rep] gene, the transcription-activator protein [TrAP] gene, the replication-enhancer protein [REn] gene, and the C4 gene) and two genes (pre-coat protein [V2] and coat protein [CP]) in virion-sense (2). BLAST analysis showed 95.2% sequence identity to Tomato leaf curl Albatinah virus (ToLCABV; FJ956700), reported earlier to infect tomato in Oman (3). Amino acid sequence comparison of the four predicted proteins (Rep, TrAP, Ren, and C4) encoded by Pap-6 shared 95, 96, 100, and 100% sequence identity, whereas virion-sense proteins (V1 and V2) shared 99% sequence identity with ToLCABV (FJ956700). According to the recommendations of the International Committee on Taxonomy of Viruses, these results indicate that the virus identified in association with papaya leaf curl disease in Oman is a variant of ToLCABV (1). All infected samples showed the presence of ToLCABV, while no hybridization was observed in healthy control DNA using ToLCABV probe. These findings are indicative of the rapid spread of diseases involving Begomovirus and betasatellites, which often result in increased host range, as is evident from this study. References: (1) C. M. Fauquet et al. Arch. Virol. 148:405, 2003. (2) L. Hanley-Bowdoin et al. Crit. Rev. Plant Sci. 18:71, 1999. (3) A. J. Khan et al. Arch. Virol. 159:445, 2013.

Tylenchulus semipenetrans is an economically important plant-parasitic nematode occurring in all citrus-producing regions of the world and causing a disease called “slow decline”. For the rapid detection of this nematode, a loop-mediated isothermal amplification (LAMP) assay was developed, based on the ribosomal DNA internal transcribed spacer sequence. The optimal condition for the LAMP assay was 65°C for 50 min. The LAMP products were confirmed using conventional polymerase chain reaction (PCR) and restriction analysis with the BamHI enzyme, and by adding SYBR Green I to the LAMP products for visual inspection. The LAMP assay was highly specific for the detection of T. semipenetrans populations from different geographical origins. It was also sensitive, detecting a tenth of the DNA from an individual specimen of T. semipenetrans, which was 10 times more sensitive than conventional PCR. The LAMP protocol was applied to natural citrus rhizosphere soil samples from several orchards in China and the results were fast, sensitive, robust, and accurate. This study is the first to provide a diagnostic tool for T. semipenetrans using DNA extracted directly from citrus rhizosphere soils. This LAMP assay could be used as a practical molecular tool to identify T. semipenetrans and diagnose slow decline disease, even in remote locations.

A method is described for the determination of the activity of endonuclease. It based on the deaggregation of gold nanoparticles (AuNPs) aggregated by the action of poly(diallyldimethylammonium chloride) (PDDA). A single-stranded DNA (ssDNA) is released after enzymatic cleavage catalyzed by endonuclease. The released fragments bind electrostatically to PDDA and inhibit the PDDA-induced aggregation of AuNPs. This is accompanied by a color change from blue to red and a decrease in the absorption ratio (A630/A520). Under the optimal conditions, this ratio increases linearly in the 0.001 to 1 U·μL−1 EcoRI endonuclease activity range. The detection limit is of 2 × 10−4 U·μL−1 which is much better or at least comparable to previous reports. The method is deemed to have wide scope in that it may be used to study other endonuclease activity (such as BamHI) by simply changing the specific recognition site of the hairpin-like DNA probe. The assay may also be employed to screening for inhibitors of EcoRI endonuclease.

Prothrombin-2 is a thrombin precursor, which plays an essential role in the conversion of fibrinogen to fibrin during the blood clotting process. In this study, we designed and constructed the human prethrombin-2 (hPT2) gene. hPT2 gene fused with a tag at the n terminal position, which contains the sequence intein followed by chitin binding domain (CBD) that useful for the purification process. The digestion process of hPT2 tag induced by changing its pH/temperature. The hPT2 codon that used in this study designed according to the preference codon of E. coli. hPT2 gene was created using the OPTIMIZER software with the addition of two side restriction at the 5’ and 3’, BamHI and XhoI respectively then were cloned by using the pMAT vector in E. coli. Moreover, hPT2 fragment ligated into an expression vector, pTWIN1, for E. coli. The result from the characterization hPT2 gene in pTWIN1 that using DNA sequencing method shown that the designed hPT2 gene cloned. Thus, the cloned hPT2 gene used as a precursor for PT2 expression in the E. coli host.

The potato phytopathogen Clavibacter michiganensis subsp. sepedonicus (Cms) is a causative agent of bacterial ring rot, which is a serious threat to crops. In EU member countries, Cms is subject to quarantine and has to be combated. The knowledge about the transmission of C. michiganensis strains is limited due to a lack of methods which could be used for epidemiological analysis. In this study, PCR melting profile (PCR MP) and variable number tandem repeat methods were used in Cms epidemiological analysis for the first time. PCR MP was based on the melting temperature analysis of BamHI restriction fragments of chromosomal DNA. Respectively, for the variable number tandem repeat (VNTR) method, six loci were identified and used in the differentiation of Cms isolates. PCR MP was used for 93 Cms isolated in Poland. Both PCR MP and VNTR methods were used for the differentiation of 47 Cms strains in this collection. Both these methods were found to be useful for the epidemiological analysis of Cms. SIGNIFICANCE AND IMPACT OF THE STUDY: The potato phytopathogen, Clavibacter michiganensis subsp. sepedonicus (Cms), is a serious threat to crops and lead to significant economic losses. The only way to control and eliminate the disease caused by this pathogen is the use of certified seed potato and strict quarantine of infected fields. Here, for the first time, two molecular typing methods (PCR melting profile (PCR MP) and variable number tandem repeat (VNTR)) were evaluated in respect of their potential in differentiation of Cms isolates. As a result, we obtained characteristic profiles of DNA fragments (PCR MP) and numeric patterns (VNTR), which enable the intraspecies genotyping of Cms strains confirming the effectiveness of PCR MP and VNTR methods in differentiation of Cms strains.

Colorimetric DNA detection is preferred over other methods for clinical molecular diagnosis because it does not require expensive equipment. In the present study, the colorimetric method based on gold nanoparticles (GNPs) and endonuclease enzyme was used for the detection of P. aeruginosa ETA gene. Firstly, the primers and probe for P. aeruginosa exotoxin A (ETA) gene were designed and checked for specificity by the PCR method. Then, GNPs were synthesized using the citrate reduction method and conjugated with the prepared probe to develop the new nano-biosensor. Next, the extracted target DNA of the bacteria was added to GNP-probe complex to check its efficacy for P. aeruginosa ETA gene diagnosis. A decrease in absorbance was seen when GNP-probe-target DNA cleaved into the small fragments of BamHI endonuclease due to the weakened electrostatic interaction between GNPs and the shortened DNA. The right shift of the absorbance peak from 530 to 562nm occurred after adding the endonuclease. It was measured using a UV-VIS absorption spectroscopy that indicates the existence of the P. aeruginosa ETA gene. Sensitivity was determined in the presence of different concentrations of target DNA of P. aeruginosa. The results obtained from the optimized conditions showed that the absorbance value has linear correlation with concentration of target DNA (R: 0.9850) in the range of 10-50ngmL-1 with the limit detection of 9.899ngmL-1. Thus, the specificity of the new method for detection of P. aeruginosa was established in comparison with other bacteria. Additionally, the designed assay was quantitatively applied to detect the P. aeruginosa ETA gene from 103 to 108CFUmL-1 in real samples with a detection limit of 320CFUmL-1.

The standard binary enzymatic assembly, which operates by inserting one DNA fragment into a plasmid, has a higher assembly success rate than the polynary enzymatic assembly, which inserts two or more fragments into the plasmid. However, it often leaves a nucleotide scar at the junction site. When a large DNA molecule is assembled stepwise into a backbone plasmid in a random piecewise manner, the scars will damage the structure of the original DNA sequence in the final assembled plasmids. Here, we propose an in vitro Seamless Stack Enzymatic Assembly (SSEA) method, a novel binary enzymatic assembly method involving a seamless strategy of splicing restriction sites via a stepwise process of multiple enzymatic reactions that does not leave nucleotide scars at the junction sites. We have demonstrated the success and versatility of this method through the assembly of 1) a 4.98 kb DNA molecule in the 5′ → 3′ direction using BamHI to generate the sticky end of the assembly entrance, 2) a 7.09 kb DNA molecule in the 3′ → 5′ direction using SmaI to generate the blunt end of the assembly entrance, and 3) an 11.88 kb DNA molecule by changing the assembly entrance.

Electrochemical methods allow fast and inexpensive analysis of enzymatic activity. Here, a simple and yet efficient "signal-on" electrochemical assay for sensitive, label-free detection of DNA-related enzyme activity was established on the basis of terminal deoxynucleotidyl transferase (TdT)-mediated extension strategy. TdT, which is a template-independent DNA polymerase, can catalyze the sequential addition of deoxythymidine triphosphate (dTTP) at the 3'-OH terminus of single-stranded DNA (ssDNA); then, the TdT-yield T-rich DNA nanowires can be employed as the synthetic template of copper nanoclusters (CuNCs). Grown DNA nanowires-templated CuNCs (noted as DNA-CuNCs) were attached onto graphene oxide (GO) surface and exhibited unique electrocatalytic activity to H2O2 reduction. Under optimal conditions, the proposed biosensor was utilized for quantitatively monitoring TdT activity, with the observed LOD of 0.1 U/mL. It also displayed high selectivity to TdT with excellent stability, and offered a facile, convenient electrochemical method for TdT-relevant inhibitors screening. Moreover, the proposed sensor was successfully used for BamHI activity detection, in which a new 3'-OH terminal was exposed by the digestion of a phosphate group. Ultimately, it has good prospects in DNA-related enzyme-based biochemical studies, disease diagnosis, and drug discovery. Graphical Abstract Extraordinary TdT-generated DNA-CuNCs are synthesized and act as a novel electrochemical sensing platform for sensitive detection of TdT and BamHI activity in biological environments.

The genetics of the Streptomyces hygroscopicus strain 10–22 is of interest due to the ability of this strain to produce antifungal compounds. Strain T110 was obtained through insertional mutagenesis of strain 10–22 and was found to have undergone DNA amplification, as determined by both conventional and pulsed-field gel electrophoresis (PFGE). pIJ702, the vector used for insertional mutagenesis, was shown to have integrated into and co-amplified with the chromosomal DNA sequence of T110, as pIJ702 hybridized predominantly with two of the three amplified BamHI fragments. The amplified DNA sequence in T110 is 10.8 kb in length and consists of 5.18 kb of Streptomyces chromosomal DNA and the entire 5.62 kb pIJ702 sequence. Sequence analysis of the 5.18 kb chromosomal sequence revealed two open reading frames, one encoding a putative IS5 family transposase and the other encoding a putative dihydroxy-acid dehydratase. Real-time PCR analysis showed that expression of the putative dehydratase gene in T110 is about 50 times greater than in the wild-type strain, consistent with the high level of amplification of this DNA region, and therefore this system has the potential for producing economically or clinically important molecules.

PubMedID: 28881255 The aim of this study was to synthesize and evaluate plasmid DNA interaction of new platinum(II) complexes with some 2-substituted benzimidazole derivatives as carrier ligands which may have potent anticancer activity and low toxicity. Twelve benzimidazole derivatives carrying indole, 2-/or 3-/or 4-methoxyphenyl, 4-methylphenyl, 3,4-dimethoxyphenyl, 3,4,5-trimethoxyphenyl, 4-methoxybenzyl, 3,4,5-trimethoxybenzyl, 3,4,5-trimethoxystyryl, 3,4,5-trimethoxybenzylthio or dimethylamino ethyl groups in their position 2 and twelve platinum(II) complexes with these carrier ligands were synthesized. The chemical structure of the platinum complexes have been characterized by their elemental analysis and FIR, 1H NMR and mass spectra and their 1H NMR and FIR spectra were interpreted by comparison with those of the ligands. The interaction of all the ligands and their complexes with plasmid DNA and their restriction endonuclease reactions by BamHI and HindIII enzymes were studied by agarose gel electrophoresis. It was determined that complex 1 [dichloro-di(2-(1H-indole-3-yl)benzimidazole)platinum(II)·2H2O] has stronger interaction than carboplatin and complex 10 [dichloro-di(2-(3,4,5-trimethoxystyryl)benzimidazole)platinum(II)·2H2O] has stronger interaction than both carboplatin and cisplatin with plasmid DNA. © 2017 Elsevier Inc. BAP-02/2015-02 We would like to thank the Research Foundation of Gazi University ( BAP-02/2015-02 ) for financial support of this work.

The gene bmp5 was obtained as codon-optimized sequence deduced from the amino acid sequence of Bmp5 from Pseudoalteromonas luteoviolacea for overexpression in E. coli. The nucleotide sequence was flanked by NdeI and BamHI restriction sites enabling subcloning into an equally digested pET28a vector for coexpression as N-terminal His6-tagged fusion protein.

International audience; Background: Viral load monitoring and early Epstein-Barr virus (EBV) DNA detection are essential in routine laboratory testing, especially in preemptive management of Post-transplant Lymphoproliferative Disorder. Targeting the repetitive BamHI-W sequence was shown to increase the sensitivity of EBV DNA quantification, but the variability of BamHI-W reiterations was suggested to be a source of quantification bias. We aimed to assess the extent of variability associated with BamHI-W PCR and its impact on the sensitivity of EBV DNA quantification using the 1st WHO international standard, EBV strains and clinical samples.Methods: Repetitive BamHI-W- and LMP2 single- sequences were amplified by in-house qPCRs and BXLF-1 sequence by a commercial assay (EBV R-gene™, BioMerieux). Linearity and limits of detection of in-house methods were assessed. The impact of repeated versus single target sequences on EBV DNA quantification precision was tested on B95.8 and Raji cell lines, possessing 11 and 7 copies of the BamHI-W sequence, respectively, and on clinical samples.ResultsBamHI-W qPCR demonstrated a lower limit of detection compared to LMP2 qPCR (2.33 log10 versus 3.08 log10 IU/mL; P = 0.0002). BamHI-W qPCR underestimated the EBV DNA load on Raji strain which contained fewer BamHI-W copies than the WHO standard derived from the B95.8 EBV strain (mean bias: - 0.21 log10; 95% CI, -0.54 to 0.12). Comparison of BamHI-W qPCR versus LMP2 and BXLF-1 qPCR showed an acceptable variability between EBV DNA levels in clinical samples with the mean bias being within 0.5 log10 IU/mL EBV DNA, whereas a better quantitative concordance was observed between LMP2 and BXLF-1 assays.Conclusions: Targeting BamHI-W resulted to a higher sensitivity compared to LMP2 but the variable reiterations of BamHI-W segment are associated with higher quantification variability. BamHI-W can be considered for clinical and therapeutic monitoring to detect an early EBV DNA and a dynamic change in viral load.

An exonuclease III (Exo III)-aided signal amplified endonuclease detection strategy was developed by employing a hairpin DNA as the substrate for endonucleases. In the presence of endonucleases, the elaborately designed stem-loop substrate was cleaved into two parts. With the help of Exo III, a single-stranded target of a molecular beacon (MB) probe was released. Subsequently, the MB would hybridize with this target to form a double-stranded DNA, opening its hairpin structure and thereby resulting in the restoration of the fluorescence signal. Owing to the presence of a recessed 3′ terminus in the formed double-stranded DNA, Exo III-aided recyclable cleavage of MBs was achieved. Eventually, an amplified fluorescence signal was observed. As a proof of concept, the fluorescence sensor of endonuclease EcoRI was designed. Under the optimized conditions, the fluorescence intensity is linear with EcoRI activity over the wide range of 1 to 80 U mL−1, with a detection limit of 0.57 U mL−1. Besides, detection of BamHI activity with satisfactory results was achieved by simply changing the endonuclease recognition sequence in the unlabelled substrate, demonstrating that the design concept can be widely adapted to other restriction endonuclease activity analysis.

Induction of endonucleolytic DNA cleavage is an essential event that links the initiating stimuli to the final effects of cells. The cleavage efficiency and thus the final yield could be affected by many factors, including structures of DNA substrates, composite structures of enzymes–substrates or enzymes–nucleic analogs and so on. However, it is not clear whether a nucleotide derivative-substituted in DNA substrates can influence the efficiency of enzymatic cleavage. To investigate the effect of sugar pucker conformation on DNA–protein interactions, we used 2′-O-methyl modified nucleotides (OMeN) to modify DNA substrates of isocaudemers BamHI and BglII in this study, and used FRET assay as an efficient method for analysis of enzyme cleavage. Experimental results demonstrated that OMeN-substituted recognition sequences influenced the cleavage rates significantly in a position-dependent manner. OMeN substitutions can reduce the cleavage as expected. Surprisingly, OMeN substitutions can also enhance the cleavage rates. The kinetics parameters of V max and K m have been obtained by fitting the Michaelis-Menten kinetic equation. These 2'-OMe nucleotides could behave as a regulatory element to modulate the enzymatic activity in vitro, and this property could enrich our understanding about the endonuclease cleavage mechanism and enhance our ability to regulate the enzymatic cleavage efficiency for applications in synthetic biology.

Herein, a double-stranded (ds) DNA microarray-based resonance light scattering (RLS) assay with multifunctional gold nanoparticle (GNP) probes has been developed for studying restriction endonuclease functionality and inhibition. Because of decreasing significantly melting temperature, the enzyme-cleaved dsDNAs easily unwind to form single-stranded (ss) DNAs. The ssDNAs are hybridized with multiplex complementary ssDNAs functionalized GNP probes followed by silver enhancement and RLS detection. Three restriction endonucleases (EcoRI, BamHI and EcoRV) and three potential inhibitors (doxorubicin hydrochloride (DOX), ethidium bromide (EB) and an EcoRI-derived helical peptide (α4)) were selected to demonstrate capability of the assay. Enzyme activities of restriction endonucleases are detected simultaneously with high specificity down to the limits of 2.0×10 −2 U/mL for EcoRI, 1.1×10 −2 U/mL for BamHI and 1.6×10 −2 U/mL for EcoRV, respectively. More importantly, the inhibitory potencies of three inhibitors are showed quantitatively, indicating that our approach has great promise for high-throughput screening of restriction endonuclease inhibitors.

The increase interest and study of underutilized and neglected crops is actual for the last years. In the study, the restriction polymorphisms of GBSSI and SSSI gene in gamma-irradiated mutant lines of amaranth was performed. To evaluate polymorphisms of restriction sites endonucleases AciI, BsaJI, FatI EcoRI, BamHI, PstI, HpaII and PciI were used. GBSSI gene responsible to amylose synthesis was digested with HpaII and PciI restriction endonucleases. Two PciI restriction sites and three HpaII restriction sites were evaluated and any changes in restriction sites were recorded. Profile changes of the SSSI gene in mutant lines C 15/1 and C 236/1 were recorded after the restriction digest by BsaJI. Restriction cleavage polymorphism was recorded after the restriction digest of segment 5250-6854 bp with restriction endonuclease FatI, too.

It is important to develop reliable and sensitive methods for assay of nuclease activity. With this goal in mind, we report a new strategy for nuclease assay by taking advantage of efficient fluorescence resonance energy transfer (FRET) between gold nanorods (GNRs) and fluorescein-tagged single-stranded DNA (FDNA). Upon mixing with GNRs, the FRET between positively charged GNRs and negatively charged FDNA caused a decrease in fluorescence of FDNA. The formation of FDNA/cDNA duplex further improved the FRET efficiency, leading to a significant decrease in fluorescence intensity. However, fluorescence is restored when FDNA1/cDNA1 hybrid was cleaved into small fragments by EcoRI endonucleases, resulting in a decrease in FRET efficiency because of weakened electrostatic interaction between GNRs and the shortened DNA fragments. Activity of EcoRI endonuclease has been real-time studied by monitoring fluorescence change with the prolonging of interaction time. Under optimized conditions, the cleaved fraction is linear with EcoRI concentration over the range of 1.0×10(-3) to 1.0×10(-1) U μL(-1), with a limit of detection of 6.5×10(-4) U μL(-1) which is much better or at least comparable to previous reports. Site-specific DNA cleavage by EcoRI endonuclease has also been verified by gel electrophoresis, fluorescence anisotropy and TEM analysis, which indicated that this method is a feasible and reasonable approach to study sequence-specific protein-DNA interactions. Assay of BamHI activity demonstrated that it is a more universally applied method for studying the activity of endonuclease. Furthermore, this fluorescence assay has been also used for studying the inhibition of EcoRI endonuclease activity. Importantly, experimental results suggested that endonuclease inhibitors can be screened by monitoring the change of fluorescence change. Therefore, this FRET assay is a simple, sensitive and effective approach to study endonuclease activity and inhibition, and as such, it promises to provide a feasible method to screen nuclease inhibitors.

The development of Lactobacillus plantarum to be used in starter cultures in the food industry has been limited because of the lack of a food-grade cloning vector for the bacterium. In this study, the plasmid pFLP1 was constructed by joining 2 DNA fragments derived from food-approved organisms. The 5.2-kb BamHI/KpnI DNA fragment of pRV566 containing the theta-type replicon of Lactobacillus sakei was ligated to the BamHI/KpnI DNA fragment of a 2.9-kb lactococcal cadmium resistance determinant amplified from pND918. The 8.1-kb newly constructed plasmid could transform L. plantarum N014, a bacteriocin-producing bacteria originally isolated from nham, a traditional Thai fermented sausage. The resulting transformant, L. plantarum N014-FLP, and its parent strain were shown to be very similar in growth rate and bacteriocin activity. In addition, the plasmid was very stable in its host bacteria under nonselective pressure for 100 generations in MRS medium and for 5 days in a nham model. These results suggest that pFLP1 is a potential food-grade cloning vector for L. plantarum.

Purpose About 10% of all gastric cancers (GCs) are Epstein-Barr virus (EBV)-associated. However, the oncogene of EBV in gastric carcinogenesis has not yet been established. In the present study, we investigated the virus-derived transcripts in the EBV-infected GC cell line to explore the viral oncogene of EBV-positive GCs. Materials and Methods We used the SNU719 cell line, a naturally derived EBV-infected GC cell line. The individual expressed sequence tags from the cDNA libraries of SNU719 were searched against the mRNA subset extracted from the GenBank data base. Sequence reaction was carried out for the EBV-associated clones. Reverse transcription-polymerase chain reaction was performed after cells were partitioned into nuclear and cytoplasmic fractions. Results Using bioinformatic tools, we selected 13 EBV-associated clones from cDNA libraries of SNU719. By sequencing analysis, we revealed that they were all associated with RPMS1, one of the BamHI-A rightward transcripts (BART) of EBV. Some BART cDNAs such as RPMS1 and A73 are known to be translated into protein in vitro, and have been shown to have some biochemical functions relevant to tumorigenesis. But, presently, the BART transcripts were expressed only in the nucleus and not in the cytoplasm, arguing against their role as messenger RNAs. Some other BART transcripts expressed in GCs (BARF0, CST, vIL, BARF1, BLLF1, and BcLF1) were also extensively detected in the nucleus. Conclusion BART transcripts are the predominant viral transcripts expressed in EBV-associated GCs, and they are located only in the nucleus. Therefore, it seems less likely that BART transcripts produce functional proteins to play a role in carcinogenesis of EBV-associated GCs.

The genome of Epstein-Barr virus (EBV), a gammaherpesvirus with potent B-cell growth-transforming ability, contains multiple copies of a 3-kb BamHI W repeat sequence; each repeat carries (i) a promoter (Wp) that initiates transformation by driving EBNA-LP and EBNA2 expression and (ii) the W1W2 exons encoding the functionally active repeat domain of EBNA-LP. The W repeat copy number of a virus therefore influences two potential determinants of its transforming ability: the number of available Wp copies and the maximum size of the encoded EBNA-LP. Here, using recombinant EBVs, we show that optimal B-cell transformation requires a minimum of 5 W repeats (5W); the levels of transforming ability fall progressively with viruses carrying 4, 3, and 2 W repeats, as do the levels of Wp-initiated transcripts expressed early postinfection (p.i.), while viruses with 1 copy of the wild-type W repeat (1W) and 0W are completely nontransforming. We therefore suggest that genetic analyses of EBV transforming function should ensure that wild-type and mutant strains have equal numbers (ideally at least 5) of W copies if the analysis is not to be compromised. Attempts to enhance the transforming function of low-W-copy-number viruses, via the activity of helper EBV strains or by gene repair, suggested that the critical defect is not related to EBNA-LP size but to the failure to achieve sufficiently strong coexpression of EBNA-LP and EBNA2 early postinfection. We further show by the results of ex vivo assays that EBV strains in the blood of infected individuals typically have a mean of 5 to 8 W copies, consistent with the view that evolution has selected for viruses with an optimal transforming function.

Friend murine leukemia virus clone A8 causes spongiform neurodegeneration in the rat brain, and the env gene of A8 is a primary determinant of neuropathogenicity. In order to narrow down the critical region within the env gene that determines neuropathogenicity, we constructed chimeric viruses having chimeric env between A8 and non-neuropathogenic 57 on the background of A8 virus. After replacement of the BamHI (at nucleotide 5715)-AgeI (at nucleotide 6322) fragment of A8 virus with the corresponding fragment of 57, neuropathogenicity was lost. In contrast, the chimeric viruses that have the BamHI (5715)-AgeI (6322) fragment of A8 induced spongiosis in 100% of infected rats at the same or slightly lower intensity than A8 virus. These results indicate that the BamHI (5715)-AgeI (6322) fragment of A8, which contains the signal sequence and the N-terminal half of RBD, is crucial for the induction of spongiform neurodegeneration. In the BamHI (5715)-AgeI (6322) fragment, seven amino acids differed between A8 and 57, one in the signal sequence and six in RBD, which suggests that these amino acids significantly contribute to the neuropathogenicity of A8.

This work proposes a new strategy for the electrochemical detection of hepatitis C virus (HCV) RNA level and identification of HCV-1b genotype based on the site-specific cleavage of BamHI endonuclease combined with gold nanoparticles (AuNPs) signal amplification. The assay procedures include the reverse transcription, polymerase chain reaction (PCR) amplification, and electrochemical detection. The samples of 244 mer sequence of HCV RNA from the highly conserved region of HCV-1a, HCV-1b, HCV-1, and HCV-6a, respectively, were first reverse transcribed into complementary cDNA and amplified by PCR. The PCR-amplified samples were then analyzed using a synthetic 21 mer DNA probe, which has been assembled on the electrode surface via a bifunctional molecule of p-aminobenzoic acid (ABA). The results demonstrated that the developed approach can be used for specifically identification of the HCV-1b genotype and selective and sensitive detection of HCV-1b cDNA (244 mer) with a detection limit as low as (3.1 ± 0.8) × 10(-22) M (less than 200 molecules; the concentration refers to the one before PCR amplification). Moreover, the developed method has an ability to discriminate the HCV-1b cDNA sequence from even single-base mismatched DNA sequence, to assay the HCV-1b cDNA level precisely from the mixture of HCV-1, HCV-1b, HCV-1a, and HCV-6a, and to detect HCV in real clinical samples. The protocol has high potential application in molecular diagnostics of HCV in clinical environments.

Restriction enzymes share little or no sequence homology with the exception of isoschizomers, or enzymes that recognize and cleave the same DNA sequence. We present here the structure of a BamHI isoschizomer, OkrAI, bound to the same DNA sequence (TATGGATCCATA) as that cocrystallized with BamHI. We show that OkrAI is a more minimal version of BamHI, lacking not only the N- and C-terminal helices but also an internal 3(10) helix and containing β-strands that are shorter than those in BamHI. Despite these structural differences, OkrAI recognizes the DNA in a remarkably similar manner to BamHI, including asymmetric contacts via C-terminal 'arms' that appear to 'compete' for the minor groove. However, the arms are shorter than in BamHI. We observe similar DNA-binding affinities between OkrAI and BamHI but OkrAI has higher star activity (at 37°C) compared to BamHI. Together, the OkrAI and BamHI structures offer a rare opportunity to compare two restriction enzymes that work on exactly the same DNA substrate.

A shuttle vector pZL1 which can replicate both in Gluconobacter oxydans and Escherichia coli was constructed based on G. oxydans DSM2003 cryptic plasmid pGOX3, a homology of G. oxydans 621H pGOX3, and E. coli cloning vector pUC18. It was found to be stably maintained in G. oxydans during the serial subcultures in the absence of antibiotic pressure for 144 h. With pGOX3 as the reference sample, the relative copy number of pZL1 in G. oxydans is 13 determined by real-time fluorescence quantitative PCR (qPCR). The copy number of pZL1 is much higher than pBBR1MCS5 in E. coli. The vector pZL1 contains six commonly used restriction endonuclease sites, HindIII, SalI, XbaI, BamHI, SmaI, KpnI, and SacI, and is easy to manipulate in molecular biology experiments. The shuttle vector was used to express a reporter protein wasabi successfully in G. oxydans DSM2003 under the control of the tufB promoter.

Pseudomonas syringae pv. eriobotryae causes serious stem canker in loquat (Eriobotrya japonica) trees. This study was conducted to determine whether plasmids are involved with its virulence. The strain NAE89, which belonged to the B group, harbored two plasmids at approximately 6.2 and 50 Mdal that caused stem canker and halo leaf spots on loquat plants. Following digestion with BamHI and ligation into the BamHI cloning site of the broad range host cosmid pLAFR3, four DNA fragments at 3.8, 6.6, 12.3, and 22.8 kb were generated. Although the plasmid-encoded virulence gene psvA was undigested with the BamHI, the halo leaf spot gene may be adjacent to the psvA gene was digested. A pLAFR3 cosmid clone was introduced into the non-pathogenic PE0 and NAE89-1 strains by triparental matings and the pathogenicity was recovered. As a result, the pLAFR3 cosmid clone was introduced into the largest size DNA fragment of 22.8 kb and determined to be the causal agent of canker on the stem of the loquat. This study revealed that the psvA gene, previously found in the 50 Mdal plasmid, was also observed in the 22.8 kb DNA fragment.

Objective: This study aimed to detect and analyze transforming growth factor alpha ( TGFA ) BamH I and Rsa I gene variants which associated with the risk factor of non-syndromic cleft palate only (NS CPO) of Indonesian subject. Methods: This was case-control study using samples from 32 NS CPO subjects and 28 control subjects. DNA was extracted from venous blood, and the TGFA gene was amplified using polymerase chain reaction technique, then digestion product from Taq I and Rsa I restriction enzyme was evaluated. Statistical analysis to determine significant differences of gene variant frequency among NS CPO subject and control was χ 2. The odds ratio (OR) was used to determine a risk factor of NS CPO. Results: The study results showed that the TGFA BamH I gene variant was not identified in NS CPO among Indonesian but TGFA Rsa I gene variant was identified. The frequency of TT/B1B1 homozygous mutant genotype was 80.0% in NS CPO subjects and 20.0% in control subjects (OR=3.857; 95% confidence interval=0.405–36.749). Conclusion: TGFA Rsa I gene can be considered a risk factor of NS CPO compared TGFA BamH 1 gene of Indonesian subjects.

This study describes the isolation of bovine herpesvirus 4 (BHV-4) from the respiratory tract of animals suffering from respiratory disease. DNA of new isolates, CH and Ni, was cleaved with BamHI, EcoRI and HindIII in restriction enzyme analysis and the fragments were identified by co-migration with the restriction profile of the reference strain Movar 33/63 cleaved with the appropriate endonuclease. Typical profiles with polyrepeti- tive DNA (prDNA) fragments were detected. In order to localize the size variation within the obtained digestion fragments, Southern blot hybridization was performed. Differences between the isolates CH, Ni were localized in both the prDNAs and the unique central part of the genome and were restricted to fragment size variation.

This work proposes a new electrochemical approach for specific detection of hepatitis C virus (HCV) based on the site-specific cleavage of BamHI endonuclease. The method was developed by immobilizing a synthetic probe DNA (a short thiol-capped single strand oligonucleotide) on the surface of a gold electrode via the –SH group at the 5′-terminus of the probe, and conjugating the electroactive label of ferroceneacetic acid (FcA) moiety to the 3′-terminus of the probe via formation of a covalent bond between the –NH2 and –COOH groups. The FcA-labeled probe was then hybridized with target cDNA (an oligonucleotide related to HCV) and cleaved by BamHI endonuclease (a site-specific endonuclease recognizing the duplex symmetrical sequence 5′–GGATCC–3′ and catalyzing double-stranded cleavage between the guanines). After digestion by BamHI, the DNA hybrid was cleaved at a specific site, and the FcA label was removed from the gold electrode surface leading to a decrease or disappearance of the electrochemical signal of the label. The extent of decrease was related to the concentration of target cDNA in solution, which forms the basis of quantitative detection of target cDNA. The detection is based on the variation of voltammetric signal (Δi) of FcA label before and after digestion with BamHI. It was demonstrated that the value of Δi has a linear relationship with the concentration of the HCV DNA (cDNA) ranging from 0.05 to 4.0 μM with a detection limit of (0.5 ± 0.2) nM at a signal/noise of 3. Moreover, the developed method has a high selectivity with ability to discriminate the complementary target DNA sequence from single-base mismatched DNA sequence, and can also be used for detection of HCV in real clinical samples. The major advantages of this enzymatic cleavage assay are its good specificity, ease of performance, and the ability to perform real-time monitoring. The proposed protocol can be taken as a general method of DNA detection and is expected to be applicable to other types of DNA analysis.

Restriction endonucleases of the PD...D/EXK family need Mg(2+) for DNA cleavage. Whereas Mg(2+) (or Mn(2+)) promotes catalysis, Ca(2+) (without Mg(2+)) only supports DNA binding. The role of Mg(2+) in DNA cleavage by restriction endonucleases has elicited many hypotheses, differing mainly in the number of Mg(2+) involved in catalysis. To address this problem, we measured the Mg(2+) and Mn(2+) concentration dependence of DNA cleavage by BamHI, BglII, Cfr10I, EcoRI, EcoRII (catalytic domain), MboI, NgoMIV, PspGI, and SsoII, which were reported in co-crystal structure analyses to bind one (BglII and EcoRI) or two (BamHI and NgoMIV) Me(2+) per active site. DNA cleavage experiments were carried out at various Mg(2+) and Mn(2+) concentrations at constant ionic strength. All enzymes show a qualitatively similar Mg(2+) and Mn(2+) concentration dependence. In general, the Mg(2+) concentration optimum (between approximately 1 and 10 mM) is higher than the Mn(2+) concentration optimum (between approximately 0.1 and 1 mM). At still higher Mg(2+) or Mn(2+) concentrations, the activities of all enzymes tested are reduced but can be reactivated by Ca(2+). Based on these results, we propose that one Mg(2+) or Mn(2+) is critical for restriction enzyme activation, and binding of a second Me(2+) plays a role in modulating the activity. Steady-state kinetics carried out with EcoRI and BamHI suggest that binding of a second Mg(2+) or Mn(2+) mainly leads to an increase in K(m), such that the inhibitory effect of excess Mg(2+) or Mn(2+) can be overcome by increasing the substrate concentration. Our conclusions are supported by molecular dynamics simulations and are consistent with the structural observations of both one and two Me(2+) binding to these enzymes.

The complete DNA sequence of plasmid pHZ1358, a widely used vector for targeted gene disruption and replacement experiments in many Streptomyces hosts, has been determined. This has allowed a detailed analysis of the basis of its structural and segregational instability, compared to the high copy number plasmid pIJ101 of Streptomyces lividans 1326 from which it was derived. A 574-bp DNA region containing sti (strong incompatibility locus) was found to be a determinant for segregational instability in its original S. lividans 1326 host, while the structural instability was found to be related to the facile deletion of the entire Escherichia coli-derived part of pHZ1358, mediated by recombination between 36-bp direct repeats. A point mutation removing the BamHI site inside the rep gene encoding a replication protein (rep*) and/or a spontaneous deletion of the 694-bp region located between rep and sti including the uncharacterized ORF85 (orf85(-)) produced little or no effect on stability. A pHZ1358 derivative (pJTU412, sti(-), rep*, orf85(-)) was then constructed which additionally lacked one of the 36-bp direct repeats. pJTU412 was demonstrated to be structurally stable but segregationally unstable and, in contrast to sti(+) pHZ1358, allowed efficient targeted gene replacement in S. lividans 1326.