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Streptomyces thermoviolaceus OPC-520 secretes two types of xylanases (StxI and StxII), an acetyl xylan esterase (StxIII), and an [alpha]-L-arabinofuranosidase (StxIV) in the presence of xylan. Xylan degradation products (mainly xylobiose) produced by the action of these enzymes entered the cell and were then degraded to xylose by an intracellular [beta]-xylosidase (BxlA). A gene cluster involved in xylanolytic system of the strain was cloned and sequenced upstream of and including a BxlA-encoding gene (bxl4). The gene cluster consisted of four different open reading frames organized in the order bxlE, bxlF, bxlG, and bxlA. Reverse transcriptase PCR analysis revealed that the gene cluster is transcribed as polycistronic mRNA. The deduced gene products, comprising BxlE (a sugar-binding lipoprotein), BxlF (an integral membrane protein), and BxlG (an integral membrane protein), showed similarity to components of the bacterial ATP-binding cassette (ABC) transport system; however, the gene for the ATP binding protein was not linked to the bxl operon. The soluble recombinant BxlE protein was analyzed for its binding activity for xylooligosaccharides. The protein showed high-level affinity for xylobiose ([K.sub.d] = 8.75 x [10.sup.-9] M) and for xylotriose ([K.sub.d] = 8.42 x [10.sup.-8] M). Antibodies raised against the recombinant BxlE recognized the detergent-soluble BxlE isolated from S. thermoviolaceus membranes. The deduced BxlF and BxlG proteins are predicted to be integral membrane proteins. These proteins contained the conserved EAA loop (between the fourth and the fifth membrane-spanning segments) which is characteristic of membrane proteins from binding-protein-dependent ABC transporters. In addition, the bxlR gene located upstream of the bxl operon was cloned and expressed in Escherichia coli. The bxlR gene encoded a 343-residue polypeptide that is highly homologous to members of the GalR/LacI family of bacterial transcriptional regulators. The purified BxlR protein specifically bound to a 4-bp inverted sequence overlapping the--10 region of the bxl operon. The binding of BxlR to the site was inhibited specifically by low concentrations of xylobiose. This site was also present in the region located between stxI and stxIV and in the upstream region of stxII. BxlR specifically bound to the regions containing the inverted sequence. These results suggest that BxlR might act as a repressor of the genes involved not only in the uptake system of xylan degradation products but also in xylan degradation of S. thermoviolaceus OPC-520.

Research has been conducted on metalloproteinase (III) induced by chitin. The cloning, sequencing and analysis of the gene which encodes this metalloproteinase are described.

Research has been conducted on the dinuclear platinum(II) complexes. The reactions of these complexes with 9-ethylguanine have been monitored in aqueous solution via (super)1 NMR spectroscopy and the results are described.

A unique chitin-binding protease, AprIV, mediates the chitinolytic activity of Alteromonas sp. strain O-7. Data show that the aprIV gene encodes a modular enzyme which consists of five domains that are involved in chitin-binding. The proteas exhibits significant chitinase activity.

The protein binding rates (PBR) of platinum‐containing agents cisplatin (CDDP), carboplatin (CBDCA) and oxaliplatin (L‐OHP) have been reported as 98%, 25–50% and 98%, respectively. To investigate the protein‐binding properties of albumin with cisplatin, carboplatin and oxaliplatin, inductively coupled plasma mass spectrometry (ICP‐MS) was used to measure their plasma concentration in rats over time. The study also examined the effects of cisplatin, carboplatin and oxaliplatin‐binding on albumin in vitro, using CD spectrometry and native‐polyacrylamide gel electrophoresis (native PAGE). The ratios of PBR to irreversible PBR, of cisplatin and oxaliplatin were 98%:98% and 90%:87%, respectively, indicating a higher affinity for irreversible binding with albumin. That of carboplatin was 25%:10%, indicating 60–70% reversible binding with albumin. The plasma protein binding rate concentrations of cisplatin, carboplatin and oxaliplatin after in vivo administration were 96%, 15% and 80%, respectively. The CD spectrometry of albumin was unaffected by cisplatin, carboplatin and oxaliplatin binding. Though similar protein binding rates were observed with oxaliplatin and cisplatin, oxaliplatin had a higher mobility rate during PAGE. It was confirmed that the binding of cisplatin and oxaliplatin with albumin affected its electric charge but not the structure. In conclusion, cisplatin and oxaliplatin bind irreversibly with albumin in plasma and may irreversibly interact with tissue protein and/or DNA. The difficulties involved with predicting the tissue concentrations of cisplatin and oxaliplatin from their plasma concentration inhibits their therapeutic drug monitoring. On the contrary, carboplatin, like some generic drugs, reversibly binds to plasma proteins. It is, therefore, possible to conduct therapeutic drug monitoring for carboplatin. [ABSTRACT FROM AUTHOR]

Presents a molecular analysis of the gene encoding a novel chitin-binding protease from Alteromonas species strain 0-7. Use of DNA sequencing analysis; Construction of expression plasmids; Purification of the modular enzyme AprIV.

• Unusual intraligand substitution of N3 for N2 of 1,2,3-triazolate. • Pt(II) migration related to the mechanism of action of the dinuclear Pt(II) compounds. • Dimerization reaction to yield a unique tetranuclear Pt(II) compound. • Presented importance of 1,2,3-triazolate derivatives as a tridentate building block. The reaction of the anticancer azolato-bridged dinuclear platinum(II) compound [{ cis -Pt(NH 3) 2 } 2 (µ-OH)(µ-1,2,3-triazolato- N1 , N2)](NO 3) 2 (AMTA) in 0.2 M DCl-D 2 O solution was monitored at 298 K using 1H NMR spectroscopy. Acid hydrolysis of AMTA first provided a dinuclear Pt(II) cationic species [{ cis -Pt(NH 3) 2 Cl} 2 (µ-1,2,3-triazolato- N1 , N2)]+ (intermediate A) which then turned into [{ cis -Pt(NH 3) 2 Cl} 2 (µ-1,2,3-triazolato- N1 , N3)]+ (intermediate B) by migration of a Pt(II) ion, initially bound to N2, to N3. Hence, intramolecular ligand substitution of N3 for N2 occurred after substitution of two chloride ligands for the hydroxido bridge. Under the reaction conditions, the intermediate A and B were unambiguously detected, and both or either of the intermediate species then dimerized by a substitution of the chlorido ligand by N3 or N2 of a partner molecule to yield an unprecedented tetranuclear Pt(II) compound [{ cis -Pt(NH 3) 2 Cl}µ-{ cis -Pt(NH 3) 2 } 2 (µ-1,2,3-triazolato- N2 , N3) 2 - N1 , N1′ ]Cl 2 (NO 3) 2 (compound 1), whose 3D structure has been determined by X-ray crystal analysis. The fact that all triazolate nitrogen atoms coordinated to 3 different Pt(II) ions indicates that 1,2,3-triazolate derivatives could be important as a unique tridentate building block for metal-organic framework. [ABSTRACT FROM AUTHOR]

Cisplatin, a simple inorganic compound, has been one of the leading antitumor drugs for near 30 years. However, cisplatin has several drawbacks such as toxicity and drug resistance. Therefore, much attention has been focused on the development of new platinum complexes with improved pharmacological properties and a broader spectrum of activity to tumors. The recent advance of research on the molecular mechanisms of drug action and the cellular mechanisms of the emergence of resistance to cisplatin assists the rational design of new classes of platinum antitumor drugs, though details of both mechanisms still remain elusive. Information on DNA binding mode of platinum complexes, recognition and repair of DNA damage is instructive. Since several not cis isomers but trans isomers and not neutral complexes but cation complexes have been found active in vitro and in vivo, the early empirical structure-activity relationships of cisplatin analogues should be reevaluated. The hypothesis that platinum complexes which bind to DNA in a different manner will have different pharmacological properties has been tested, and now cationic multi-nuclear complexes and even trans-platinum complexes comprise unique classes of antitumor platinum-based agents with chemical and biological properties different from cisplatin. These new type platinum complexes are often effective to acquired cisplatin resistant tumor cells. In conclusion, the following complexes appear to offer great potential as new antitumor agents: (1) Complexes with distinctively different DNA interaction modes from cisplatin, which may circumvent intrinsic and acquired resistance to cisplatin through eluding the vigilance of DNA repair systems and (2) complexes with different tissue distribution or mechanisms of membrane transport which may exhibit a different spectrum of activity.