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Small macrocyclic peptides are promising candidates for new anti-infective drugs. To date, such peptides have been poorly studied in the context of anti-virulence targets. Using phage display and a self-designed peptide library, we identified a cyclic heptapeptide that can bind the carbon storage regulator A (CsrA) from Yersinia pseudotuberculosis and displace bound RNA. This disulfide-bridged peptide, showed an IC50 value in the low micromolar range. Upon further characterization, cyclisation was found to be essential for its activity. To increase metabolic stability, a series of disulfide mimetics were designed and a redox-stable 1,4-disubstituted 1,2,3-triazole analogue displayed activity in the double-digit micromolar range. Further experiments revealed that this triazole peptidomimetic is also active against CsrA from Escherichia coli and RsmA from Pseudomonas aeruginosa. This study provides an ideal starting point for medicinal chemistry optimization of this macrocyclic peptide and might pave the way towards broad-acting virulence modulators.

We designed a library of 24 cyclic peptides containing arginine (R) and tryptophan (W) residues in a sequential manner [R

Linusorbs (LOs) and peptides from flaxseed protein have documented biological activity, such as angiotensin-converting enzyme inhibition, antioxidant, anticancer, and immunosuppressive activities, but their mechanism and structure-related bioactivity have not been summarized previously. Therefore, this study reviews the structure, composition, bioavailability, and health benefits of flaxseed peptides and LOs as well as peptide generation and LO modification. However, these peptides and LOs are long linear and cyclic structures, which affect the absorption and bioavailability of these substances in living beings and, thus, impair their overall efficiency and pharmacological effectiveness. Therefore, the development of novel strategies for optimizing the bioavailability of these peptide compounds is critical to ensure their successful application and delivery to the target sites via specially designed methods that will significantly improve their

Anti-cyclic citrullinated peptide antibody testing is used to diagnose rheumatoid arthritis and associated with interstitial lung disease in RA. Herein, we investigate the relationship between anti-CCP antibody and ILD in SSc. We performed a retrospective analysis at a tertiary medical center between 2005 and 2019. Patients with SSc, systemic lupus erythematosus, and polymyositis/dermatomyositis (PM/DM) were evaluated for anti-CCP antibody and ILD. Additionally, medical records of SSc patients with ILD were reviewed. SSc patients had the highest anti-CCP antibody positivity rate compared to those with SLE and PM/DM. The incidence of ILD was higher in SSc patients with anti-CCP antibody than in those without. The usual interstitial pneumonia (UIP) incidence was higher in the anti-CCP antibody-positive group than in the anti-CCP antibody-negative group. The DLCO was lower in the anti-CCP antibody-positive group than in the anti-CCP antibody-negative group. On multivariable analysis, factors associated with SSc-ILD were anti-CCP antibody or rheumatoid factor (β coefficient, 2.652 [95% CI 1.472 to 4.776]) and anti-Scl70 antibody (β coefficient, 4.011 [95% CI 2.142 to 7.508]). Anti-CCP antibody may be associated with a higher incidence of ILD in SSc. SSc patients with anti-CCP antibody may have more UIP pattern and lower DLCO.Trial Registration Retrospectively registered.

LC-MS and molecular networking analyses of the extract of the marine sponge Psammocinia sp. indicated the presence of two new compounds with multiple halogens. LC-MS-guided isolation yielded cyclic peptides, cyclopsammocinamides A (1) and B (2), in an enantiomeric relationship to cyclocinamide A (3). Planar structures of 1 and 2 were elucidated by NMR and mass spectroscopic analyses and the absolute configurations of the amino acid residues were determined using Marfey's method with their acid hydrolysates. The sponge extract exhibited cytotoxicity and the bioassay-guided isolation afforded a dimeric dilactone macrolide, swinholide A, as the cytotoxic compound.

Tumor‑associated (TA) autoantibodies are considered to be promising biomarkers for the early detection of cancer, prior to the development of clinical symptoms. In the present study, a novel TA autoantibody was detected, which may prove to be useful as a diagnostic marker of human HCC using an HBx‑transgenic (HBx‑tg) hepatocellular carcinoma (HCC) mouse model. Its target antigen was identified as the bromodomain‑containing protein 2 (BRD2), a transcriptional regulator that plays a pivotal role in the transcriptional control of diverse genes. BRD2 was upregulated in HCC tissues of the H‑ras12V‑tg mouse and human subjects, as demonstrated using western blotting or immunohistochemical analysis, with the BRD2 autoantibody. In addition, the truncated BRD2 reactive to the BRD2 autoantibody was detected in tumor cell‑derived exosomes, which possibly activated TA immune responses and the generation of autoantibodies. For the detection of the serum BRD2 autoantibody, epitope mimicries of autoantigenic BRD2 were screened from a random cyclic peptide CXsub7/subC library with the BRD2 autoantibody. A mimotope with the sequence of CTSVFLPHC, which was cyclized by one pair of cysteine residues, exhibited high affinity to the BRD2 autoantibody and competitively inhibited the binding of the autoantibody to the cellular BRD2 antigen. The use of this cyclic peptide as a capture antigen in human serum enzyme‑linked immunosorbent assay allowed the distinction of patients with HCC from healthy subjects with 64.41% sensitivity and 82.42% specificity (area under the ROC curve, 0.7761), which is superior to serum alpha‑fetoprotein (AFP; 35.83% sensitivity; 100% specificity; area under the ROC curve, 0.5337) for the diagnosis of HCC. In addition, the detection of the BRD2 autoantibody combined with other autoantibody biomarkers or AFP has increased the accuracy of HCC diagnosis, suggesting that the combinational detection of cancer biomarkers, including the BRD2 autoantibody, is a promising assay for HCC diagnosis.

The synthesis of cyclotetrapeptides analogues of the natural products tentoxin and versicotide D was achieved in good yield by solid phase peptide synthesis (SPPS) of their linear precursors and solution phase cyclization. All the cyclopeptides and several open precursors were evaluated as herbicides. Five cyclopeptides and five lineal peptides showed a significant inhibition (>70%) of Ryegrass seed’s radicle growth at 67 μg/mL. The evaluation at lower concentrations (4–11 μM) indicates two cyclopeptides analogs of tentoxin, which present one (N-Methyl-d-Phe), and two N-MeAA (N-Methyl-Ala and N-Methyl-Phe), respectively, as the most active of them, showing remarkable phytotoxic activity. In two cases, the open precursors are as active as their corresponding cyclopeptide. However, many linear peptides are inactive and their cyclization derivatives showed herbicidal activity. In addition, two cyclopeptide analogues of versicotide D showed more improved activity than the natural product. The results indicate that the peptide sequence, the amino acid stereochemistry and the presence of N-methyl group have important influence on the phytotoxic activity. Moreover, several compounds could be considered as lead candidates in the development of bioherbicides.

Backbone-dependent rotamer libraries are commonly used to assign the side chain dihedral angles of amino acids when modeling protein structures. Most rotamer libraries are created by curating protein crystal structure data and using various methods to extrapolate the existing data to cover all possible backbone conformations. However, these rotamer libraries may not be suitable for modeling the structures of cyclic peptides and other constrained peptides because these molecules frequently sample backbone conformations rarely seen in the crystal structures of linear proteins. To provide backbone-dependent side chain information beyond the α-helix, β-sheet, and PPII regions, we used explicit-solvent metadynamics simulations of model dipeptides to create a new rotamer library that has high coverage in the (ϕ, ψ) space. Furthermore, this approach can be applied to build high-coverage rotamer libraries for noncanonical amino acids. The resulting Metadynamics of Dipeptides for Rotamer Distribution (MEDFORD) rotamer library predicts the side chain conformations of high-resolution protein crystal structures with similar accuracy (~80%) to a state-of-the-art rotamer library. Our ability to test the accuracy of MEDFORD at predicting the side chain dihedral angles of amino acids in noncanonical backbone conformation is restricted by the limited structural data available for cyclic peptides. For the cyclic peptide data that are currently available, MEDFORD and the state-of-the-art rotamer library perform comparably. However, the two rotamer libraries indeed make different rotamer predictions in noncanonical (ϕ, ψ) regions. For noncanonical amino acids, the MEDFORD rotamer library predicts the χ

Two new antiplasmodial peptides, named koshidacins A (

A family of novel cyclic lipopeptides named tasikamides A􀀀 H (Tsk A􀀀 H) were discovered recently in Streptomyces tasikensis P46. Aside from the unique cyclic pentapeptide scaffold shared by the tasikamides, Tsk A􀀀 C contain a hydrazone bridge that connects the cyclic pentapeptide to the lipophilic alkyl 5- hydroxylanthranilate (AHA) moiety. Here we report the production of tasikamides I􀀀 K (Tsk I􀀀 K) by a mutant strain of S. tasikensis P46 that overexpresses two pathway-specific transcription regulators. Unlike Tsk A􀀀 C, Tsk I􀀀 K feature a rare enaminone-bridge that links the cyclic peptide scaffold to the AHA moiety. Our experimental data suggest that Tsk I􀀀 K are generated by the coupling of two biosynthetic pathways via a nonenzymatic condensation reaction between an arylamine and a β-keto aldehyde-containing precursor. The results underscore the nucleophilic and electrophilic reactivity of the β-keto aldehyde moiety and its ability to Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version We acknowledge the generous funding support from the Ministry of Education of Singapore (ARC Tier 2 grant (T2EP30221-0029) awarded to Z.-X.L.) and National Research Foundation of Singapore (SBP01 grant awarded to Z.-X.L.).

Cell-permeable, macrocyclic peptides antagonize either the active or the inactive states of Gα s to fine-tune signaling.

An alpha helical turn can be reproduced in a cyclic pentapeptide if the first and fifth amino acid sidechains are correctly joined. Here structural studies (CD, NMR

We have synthesised short analogues of the marine antimicrobial peptide Turgencin A from the colonial Arctic ascidian Synoicum turgens. In this study, we focused on a central, cationic 12-residue Cys-Cys loop region within the sequence. Modified (tryptophan- and arginine-enriched) linear peptides were compared with Cys-Cys cyclic derivatives, and both linear and Cys-cyclic peptides were N-terminally acylated with octanoic acid (C8), decanoic acid (C10) or dodecanoic acid (C12). The highest antimicrobial potency was achieved by introducing dodecanoic acid to a cyclic Turgencin A analogue with low intrinsic hydrophobicity, and by introducing octanoic acid to a cyclic analogue displaying a higher intrinsic hydrophobicity. Among all tested synthetic Turgencin A lipopeptide analogues, the most promising candidates regarding both antimicrobial and haemolytic activity were C12-cTurg-1 and C8-cTurg-2. These optimized cyclic lipopeptides displayed minimum inhibitory concentrations of 4 µg/mL against Staphylococcus aureus, Escherichia coli and the fungus Rhodothorula sp. Mode of action studies on bacteria showed a rapid membrane disruption and bactericidal effect of the cyclic lipopeptides. Haemolytic activity against human erythrocytes was low, indicating favorable selective targeting of bacterial cells.

Lactic acid bacteria (LAB) are ubiquitous bacteria associated with spontaneous lactic fermentation of vegetables, dairy and meat products. They are generally recognized as safe (GRAS), and they are involved in transformation of probiotic lacto-fermented foods, highly desired for their nutraceutical properties. The antifungal activity is one of the exciting properties of LAB, because of its possible application in food bio-preservation, as alternative to chemical preservatives. Many recent research works have been developed on antifungal activity of LAB, and they demonstrate their capacity to produce various antifungal compounds, (i.e. organic acids, PLA, proteinaceous compounds, peptides, cyclic dipeptides, fatty acids, and other compounds), of different properties (hydrophilic, hydrophobic and amphiphilic). The effectiveness of LAB in controlling spoilage and pathogenic fungi, demonstrated in different agricultural and food products, can be due to the synergistic effect between their antifungal compounds of different properties; where the amphiphilic-compounds allow the contact between the target microbial cell (hydrophilic compartment) and antifungal hydrophobic-compounds. Further studies on the interaction between compounds of these three properties are to de be developed, in order to highlight more their mechanism of action, and make LAB more profitable in improving shelf life and nutraceutical properties of foods.

In recent years, cyclic peptides have attracted much attention due to their chemical and enzymatic stability, low toxicity, and easy modification. In general, the self-assembled nanostructures of cyclic peptides tend to form nanotubes in a cyclic stacking manner through hydrogen bonding. However, studies exploring other assembly strategies are scarce. In this context, we proposed a new assembly strategy based on cyclic peptides with covalent self-assembly. Here, cyclic peptide-(DPDPDP) was rationally designed and used as a building block to construct new assemblies. With cyclo-(DP)3 as the structural unit and 2,2′-diamino-N-methyldiethylamine as the linker, positively charged nanospheres ((CP)6NS) based on cyclo-(DP)3 were successfully constructed by covalent self-assembly. We assessed their size and morphology by scanning electron microscopy (SEM), TEM, and DLS. (CP)6NS were found to have a strong positive charge, so they could bind to siRNA through electrostatic interactions. Confocal microscopy analysis and cell viability assays showed that (CP)6NS had high cellular internalization efficiency and low cytotoxicity. More importantly, real-time polymerase chain reaction (PCR) and flow cytometry analyses indicated that (CP)6NS-siRNA complexes potently inhibited gene expression and promoted tumor cell apoptosis. These results suggest that (CP)6NS may be a potential siRNA carrier for gene therapy.

Rheumatoid arthritis (RA) is an autoimmune disease characterized by autoantibodies against citrullinated antigens. The anti-cyclic citrullinated peptide (Anti-CCP) test is commonly used to diagnose rheumatoid arthritis, whereas the anti-mutated citrullinated vimentin (Anti-MCV) is another anti-citrullinated antibody that reacts with mutated citrullinated vimentin. Therefore, we aimed to assess the diagnostic value of anti-MCV antibodies in RA patients and their relation to disease activity. This study included 60 RA patients and 25 normal controls. The disease activity of RA patients was assessed by disease activity score (DAS-28). ELISA was used to test patients and controls for anti-MCV and anti-CCP. The level of anti-MCV was significantly higher among patients with RA compared to the control group (1.56 ± 0.56 vs. 1.20 ± 0.19 mol/l; P0.001). Anti-MCV at cut-off point of1.2 mol/l had 76% sensitivity and 100% specificity, with an overall diagnostic accuracy of 83.2% for diagnosing RA. Regarding early RA diagnosis, anti-MCV at the cut-off point was1.2 mol/l with 70% sensitivity and 100% specificity. For diagnosis of late RA, the cut-off point was1.2 mol/l, with 93.3% sensitivity and 100% specificity, whereas the overall diagnostic accuracy was 96.3%. In this study, patients with positive anti-CCP had a marginally higher level of anti-MCV compared to those with negative anti-CCP (1.64 ± 0.28 vs. 1.48 ± 0.73 mol/l; P= 0.29). We concluded that serum levels of Anti-MCV can be used as a diagnostic test in RA. The increased serum levels of Anti-MCV, demonstrated the importance of Anti-MCV as an independent serum marker in predicting the outcome of RA.

International audience; Plant protection is mainly based on the application of synthetic pesticides to limit yield losses resulting from diseases. However, the use of more eco-friendly strategies for sustainable plant protection has become a necessity that could contribute to controlling pathogens through a direct antimicrobial effect and/or an induction of plant resistance. Three different families of natural or bioinspired compounds originated from bacterial or fungal strains have been evaluated to protect wheat against powdery mildew, caused by the biotrophic Blumeria graminis f.sp. tritici (Bgt). Thus, three bio-inspired mono-rhamnolipids (smRLs), three cyclic lipopeptides (CLPs, mycosubtilin (M), fengycin (F), surfactin (S)) applied individually and in mixtures (M + F and M + F + S), as well as a chitosan oligosaccharide (COS) BioA187 were tested against Bgt, in planta and in vitro. Only the three smRLs (Rh-Eth-C12, Rh-Est-C12 and Rh-Succ-C12), the two CLP mixtures and the BioA187 led to a partial protection of wheat against Bgt. The higher inhibitor effects on the germination of Bgt spores in vitro were observed from smRLs Rh-Eth-C12 and Rh-Succ-C12, mycosubtilin and the two CLP mixtures. Taking together, these results revealed that such molecules could constitute promising tools for a more eco-friendly agriculture.

Cyanobactins are linear and cyclic post-translationally modified peptides. Here we show that the prenyl-D-Arg-containing autumnalamide A is a member of the cyanobactin family. Biochemical assays demonstrate that the AutF prenyltransferase targets the guanidinium moiety in arginine and homoarginine and is a useful tool for biotechnological applications.

Staphylococcus aureus (Sa) is an opportunistic pathogen capable of causing various infections ranging from superficial skin infections to life-threatening severe diseases including pneumonia and sepsis. Sa produces biofilms readily on biotic and abiotic surfaces. Biofilm cells are embedded in a protective polysaccharide matrix and show an innate resistance to antibiotics, disinfectants, and clearance by host defenses. Additionally, biofilms serve as a source for systemic dissemination. Moreover, infections associated with biofilms may result in longer hospitalizations, a need for surgery, and may even result in death. Agents that inhibit the formation of biofilms and virulence without affecting bacterial growth to avoid the development of drug resistance could be useful for therapeutic purposes. In this regard, we identified and purified a small cyclic peptide, gurmarin, from a plant source that inhibited the formation of Sa biofilm under in vitro growth conditions without affecting the viability of the bacterium. The purified peptide showed a predicted molecular size of ~4.2 kDa on SDS-PAGE. Transcriptomic analysis of Sa biofilm treated with peptide showed 161 differentially affected genes at a 2-fold change, and some of them include upregulation of genes involved in oxidoreductases and downregulation of genes involved in transferases and hydrolases. To determine the inhibitory effect of the peptide against Sa biofilm formation and virulence in vivo, we used a rat-implant biofilm model. Sa infected implants with or without peptide were placed under the neck skin of rats for seven days. Implants treated with peptide showed a reduction of CFU and lack of edema and sepsis when compared to that of control animals without peptide. Taken together, gurmarin peptide blocks Sa biofilm formation in vitro and in vivo and can be further developed for therapeutic use.

Colorectal cancer (CRC) is the third most commonly diagnosed form of cancer worldwide. Recent studies have indicated a strong correlation between microbial imbalance and the development of CRC. An abundance of

Cells in microbial communities on surfaces live and divide in close proximity, which greatly enhances the potential for social interactions. Spatiogenetic structures manifest through competitive and cooperative interactions among the same and different genotypes within a shared space, and extracellular secretions appear to function dynamically at the forefront. A previous experimental evolution study utilizing Pseudomonas fluorescens Pf0-1 colonies demonstrated that diverse mutations in the rsmE gene are repeatedly and exclusively selected through the formation of a dominant spatial structure. RsmE’s primary molecular function is translation repression, and its homologs regulate various social and virulence phenotypes. Pseudomonas spp. possess multiple paralogs of Rsm proteins, and RsmA, RsmE, and RsmI are the most prevalent. Here, we demonstrate that the production of a mucoid polymer and a biosurfactant are exclusively regulated through RsmE, contradicting the generalized notion of functional redundancy among the Rsm paralogs. Furthermore, we identify the biosurfactant as the cyclic lipopeptide gacamide A. Competition and microscopy analyses show that the mucoid polymer is solely responsible for creating a space of low cellular density, which is shared exclusively by the same genotype. Gacamide A and other RsmE-regulated products appear to establish a physical boundary that prevents the encroachment of the competing genotype into the newly created space. Although cyclic lipopeptides and other biosurfactants are best known for their antimicrobial properties and reducing surface tension to promote the spreading of cells on various surfaces, they also appear to help define spatial structure formation within a dense community.IMPORTANCEIn densely populated colonies of the bacterium Pseudomonas fluorescens Pf0-1, diverse mutations in the rsmE gene are naturally selected by solving the problem of overcrowding. Here, we show that RsmE-regulated secretions function together to create and protect space of low cell density. A biosurfactant generally promotes the spreading of bacterial cells on abiotic surfaces, however, it appears to function atypically within a crowded population by physically defining genotypic boundaries. Another significant finding is that these secretions are not regulated by RsmE’s paralogs that share high sequence similarity. The experimental pipeline described in this study is highly tractable and should facilitate future studies to explore additional RsmE-regulated products and address why RsmE is functionally unique from its paralogs.

The structural characterization of protein-peptide interactions is fundamental to elucidating biological processes and designing peptide drugs. Molecular dynamics (MD) simulations are extensively used to study biomolecular systems. However, simulating the protein-peptide binding process is usually quite expensive. Based on our previous studies, herein, we propose a simple and effective method to predict the binding site and pose of the peptide simultaneously using high-temperature (high

Circular RNA (circRNA) is a single-stranded circular closed RNA molecule formed from linear RNA through reverse splicing. circRNAs are stable, highly conserved, and tissue-specific. circRNAs can regulate physiological and pathological processes through various mechanisms such as formation of competing endogenous RNA and interaction with binding proteins. It has been recently revealed that circRNAs can be translated into peptides and proteins to participate in the initiation and development of cancer. circRNAs are promising diagnostic and prognostic markers for human cancers as well as potential drug targets for cancer therapy. This review summarized the research progresses related to circRNA-encoded peptides and proteins in a variety of cancers. These peptides and proteins are translated through two different mechanisms that depend on internal ribosome entry site and m6A, respectively. We also summarized the potential use of circRNA-encoded peptides and proteins in the diagnosis, treatment, prognosis and mechanistic studies of various cancers.

Peptides are ideal candidates for the development of antiviral therapeutics due to their specificity, chemical diversity and potential for highly potent, safe, molecular interventions. By restricting conformational freedom and flexibility, cyclic peptides frequently increase peptide stability. Viral targets are often very challenging as their evasive strategies for infectivity can preclude standard therapies. In recent years, several peptides from natural sources mitigated an array of viral infections. In parallel, short peptides derived from key viral proteins, modified with chemical groups such as lipids and cell-penetrating sequences, led to highly effective antiviral inhibitor designs. These strategies have been further developed during the recent COVID-19 pandemic caused by the novel coronavirus SARS-CoV-2. Several anti-SARS-CoV-2 peptides are gaining ground in pre-clinical development. Overall, peptides are strong contenders for lead compounds against many life-threatening viruses and may prove to be the key to future efforts revealing viral mechanisms of action and alleviating their effects.

Cancer has been a grand challenge in global health. However, the complex tumor microenvironment generally limits the access of therapeutics to deeper tumor cells, leading to tumor recurrence. To conquer the limited penetration of biological barriers, cell-penetrating peptides (CPPs) have been discovered with excellent membrane translocation ability and have emerged as useful molecular transporters for delivering various cargoes into cells. However, conventional linear CPPs generally show compromised proteolytic stability, which limits their permeability across biological barriers. Thus, the development of novel molecular transporters that can penetrate biological barriers and exhibit enhanced proteolytic stability is highly desired to promote drug delivery efficiency in biomedical applications. We have previously synthesized a panel of short cyclic CPPs with aromatic crosslinks, which exhibited superior permeability in cancer cells and tissues compared to their linear counterparts. Here, a concise protocol is described for the synthesis of the fluorescently labeled cyclic polyarginine R8 peptide and its linear counterpart, as well as key steps for investigating their cell permeability.

We report a versatile and durable method for synthesizing highly

ContextSome reports suggest that acromegaly in elderly patients has a more benign clinical behavior and could have a better response to first-generation long-acting somatostatin receptor ligands (SRL). However, there is no specific therapeutic protocol for this special subgroup of patients.ObjectiveThis study aimed at identifying predictors of response to SRL in elderly patients.DesignMulticentric retrospective nationwide study of patients diagnosed with acromegaly at or over the age of 65 years.ResultsOne-hundred and eighteen patients (34 men, 84 women, mean age at diagnosis 71.7 ± 5.4 years old) were included. Basal insulin-like growth factor type 1 (IGF-1) above the upper limit of normal (ULN) and growth hormone (GH) levels (mean ± SD) were 2.7 ± 1.4 and 11.0 ± 11.9 ng/ml, respectively. The mean maximal tumor diameter was 12.3 ± 6.4 mm, and up to 68.6% were macroadenoma. Seventy-two out of 118 patients (61.0%) underwent surgery as primary treatment. One-third of patients required first-line medical treatment due to a rejection of surgical treatment or non-suitability because of high surgical risk. After first-line surgery, 45/72 (63.9%) were in disease remission, and 16/34 (46.7%) of those treated with SRL had controlled disease. Patients with basal GH at diagnosis ≤6 ng/ml had lower IGF-1 levels and had smaller tumors, and more patients in this group reached control with SRL (72.7% vs. 33.3%; p < 0.04) [OR: 21.3, IC: 95% (2.4–91.1)], while male patients had a worse response [OR: 0.09, IC 95% (0.01–0.75)]. The predictive model curve obtained for SRL response showed an AUC of 0.82 CI (0.71–0.94).ConclusionsThe most frequent phenotype in newly diagnosed acromegaly in the elderly includes small adenomas and moderately high IGF-1 levels. GH at diagnosis ≤6 ng/ml and female gender, but not age per se, were associated with a greater chance of response to SRL.

Lanthipeptides are a class of cyclic peptides characterized by the presence of one or more lanthionine (Lan) or methyllanthionine (MeLan) thioether rings. These cross-links are produced by α,β-unsaturation of Ser or Thr residues in peptide substrates by dehydration, followed by a Michael-type conjugate addition of Cys residues onto the dehydroamino acids. Lanthipeptides may be broadly classified into at least five different classes, and the biosynthesis of classes I-IV lanthipeptides requires catalysis by LanC cyclases that control both the site-specificity and the stereochemistry of the conjugate addition. In contrast, there are no current examples of LanCs that occur in class V biosynthetic clusters, despite the presence of lanthionine rings in these compounds. In this work, bioinformatics-guided co-occurrence analysis identifies more than 240 putative class V lanthipeptide clusters that contain a LanC cyclase. Reconstitution studies demonstrate that the cyclase-catalyzed product is notably distinct from the product formed spontaneously. Stereochemical analysis shows that the cyclase diverts the final product to a configuration that is distinct from one that is energetically favored. Structural characterization of the final product by multi-dimensional NMR spectroscopy reveals that it forms a helical stapled peptide. Mutational analysis identified a plausible order for cyclization and suggests that enzymatic rerouting to the final structure is largely directed by the construction of the first lanthionine ring. These studies show that lanthipeptide cyclases are needed for the biosynthesis of some constrained peptides, the formations of which would otherwise be energetically unfavored.

Cyclic peptides are among the most diverse architectures for current drug discovery efforts. Their size, stability, and ease of synthesis provide attractive scaffolds to engage and modulate some of the most challenging targets, including protein-protein interactions and those considered to be "undruggable". With a variety of sophisticated screening technologies to produce libraries of cyclic peptides, including phage display, mRNA display, split intein circular ligation of peptides, and

Here we explore electrochemical dethiylation in processes relevant to Native Chemical Ligation (NCL). NCL's reliance on the redox active amino acid cysteine and β-mercaptamine derivatives suggests a potential role for electrochemistry. We show that the application of a 1 V potential to platinum electrodes in 0.15 M TCEP solution is sufficient to convert Cys to Ala in cyclic peptides, and to cleave the 2-mercapto-2-phenethyl class of acyl transfer auxiliary.

Gram-positive bacteria produce small autoinducing peptides (AIPs), which act to regulate expression of genes that promote adaptive traits, including virulence. The Gram-positive pathogen Staphylococcus aureus generates a cyclic AIP that controls expression of virulence factors via the accessory gene regulatory (Agr) system. S. aureus strains belong to one of four Agr groups (Agr-I, -II, -III, and -IV); each group harbors allelic variants of AgrD, the precursor of AIP. In a prior screen for S. aureus virulence factors, we identified MroQ, a putative peptidase. A ΔmroQ mutant closely resembled a Δagr mutant and had significant defects in AIP production in an Agr-I strain. Here, we show that expression of AgrD-I in a ΔmroQ mutant leads to accumulation of an AIP processing intermediate at the membrane that coincides with a loss of secreted mature AIP, indicating that MroQ promotes maturation of AgrD-I. MroQ is conserved in all Agr sequence variants, suggesting either identical function among all Agr types or activity specific to Agr-I strains. Our data indicate that MroQ is required for AIP maturation and activity in Agr-I, -II, and -IV strains irrespective of background. However, MroQ is not required for Agr-III activity despite an identifiable role in peptide maturation. Isogenic Δagr and Δagr ΔmroQ strains complemented with Agr-I to -IV validated the critical role of MroQ in the generation of active AIP-I, -II, and -IV but not AIP-III. These findings were reinforced by skin infection studies with mice. Our data substantiate the prevailing model that MroQ is a mediator of cyclic peptide maturation.

Stapling of peptides renders them better drug candidates. We report a new peptide staple resembling the natural metabolite lanthionine ketenamine. The strategy is orthogonal to canonical amino acids, proceeds in water and allows for tailored linkers. We applied the approach to the identification of cyclic peptide inhibitiors of the Zika virus protease. The right linker length of the peptide staple proved crucial for maximising activity. The best stapled peptide showed one order of magnitude stronger enzyme inhibition than its linear analogue.

Ilamycins/rufomycins are marine cycloheptapeptides containing unusual amino acids. Produced by Streptomyces sp., these compounds show potent activity against a range of mycobacteria, including multidrug-resistant strains of Mycobacterium tuberculosis. The cyclic peptides target the AAA+ protein ClpC1 that, together with the peptidases ClpP1/ClpP2, forms an essential ATP-driven protease. Derivatives of the ilamycins with a simplified tryptophane unit are synthesized in a straightforward manner. The ilamycin derivative 26 with a cyclic hemiaminal structure is active in the nM-range against several mycobacterial strains and shows no significant cytotoxicity. In contrast, derivative 27, with a glutamic acid at this position, is significantly less active, with MICs in the mid µM-range. Detailed investigations of the mode of action of 26 indicate that 26 deregulates ClpC1 activity and strongly enhances ClpC1-WT ATPase activity. The consequences of 26 on ClpC1 proteolytic activities were substrate-specific, suggesting dual effects of 26 on ClpC1-WT function. The positive effect relates to ClpC1-WT ATPase activation, and the negative to competition with substrates for binding to the ClpC1 NTD.

Cyclic peptides have attracted attention as a promising pharmaceutical modality due to their potential to selectively inhibit previously undruggable targets, such as intracellular protein–protein interactions. Poor membrane permeability is the biggest bottleneck hindering successful drug discovery based on cyclic peptides. Therefore, the development of computational methods that can predict membrane permeability and support elucidation of the membrane permeation mechanism of drug candidate peptides is much sought after. In this study, we developed a protocol to simulate the behavior in membrane permeation steps and estimate the membrane permeability of large cyclic peptides with more than or equal to 10 residues. This protocol requires the use of a more realistic membrane model than a single-lipid phospholipid bilayer. To select a membrane model, we first analyzed the effect of cholesterol concentration in the model membrane on the potential of mean force and hydrogen bonding networks along the direction perpendicular to the membrane surface as predicted by molecular dynamics simulations using cyclosporine A. These results suggest that a membrane model with 40 or 50 mol % cholesterol was suitable for predicting the permeation process. Subsequently, two types of membrane models containing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and 40 and 50 mol % cholesterol were used. To validate the efficiency of our protocol, the membrane permeability of 18 ten-residue peptides was predicted. Correlation coefficients of R > 0.8 between the experimental and calculated permeability values were obtained with both model membranes. The results of this study demonstrate that the lipid membrane is not just a medium but also among the main factors determining the membrane permeability of molecules. The computational protocol proposed in this study and the findings obtained on the effect of membrane model composition will contribute to building a schematic view of the membrane permeation process. Furthermore, the results of this study will eventually aid the elucidation of design rules for peptide drugs with high membrane permeability.

Cyanobacteria of the

One new cyclopeptide was isolated from the ethyl acetate fraction of the 75% EtOH extract of Selaginella tamariscina by various column chromatography methods(HP-20, polyamide and semi-preparative HPLC). Its structure was identified as selapeptin A(1) by extensive spectroscopic analysis(HR-ESI-MS, 1 D and 2 D NMR). Compound 1 was evaluated for cytotoxic activities by MTT assay. It showed potent cytotoxic activity against B16 F10 with the inhibition rate of 51.57%±4.34% at 40 μmol·L~(-1) while had no impacts on MDA-MB-231 and MDA-MB-468 at 100 μmol·L~(-1).

Acute myocardial infarction (AMI) is one of the most common ischemic heart diseases. However, lack of sufficient drug concentration (in the ischemic heart) is the major factor of treatment failure. It is urgent for researchers to engineer novel drug delivery systems to enhance the targeted delivery of cardioprotective agents. The aim of the present study was to investigate the anti-AMI ability of calycosin (CAL) and tanshinone (TAN) co-loaded; mitochondrion-targeted tetrapeptide (MTP) and cyclic arginyl-glycyl-aspartic acid (RGD) peptide co-modified nano-system.: We prepared CAL and TAN combined lipid-polymer hybrid nano-system, and RGD was modified to the system to achieve RGD-CAL/TAN NS. MTP-131 was conjugated with PEG and modified onto the nanoparticles to achieve dual ligands co-modified MTP/RGD-CAL/TAN NS. The physicochemical properties of nano-systems were characterized. The AMI therapy ability of the systems was investigated in AMI rats' model. The size of MTP/RGD-CAL/TAN NS was 170.2 ± 5.6 nm, with a surface charge of -18.9 ± 1.9 mV. The area under the curve (AUC) and blood circulation half-life (T

Somatostatin analogues, suchas octreotide and lanreotide, are commonly used in the management of enterocutaneous fistula. We report a case of severe and prolonged hyperglycemia that occurred in a patient after receiving a one-time dose of lanreotide, who had previously been stable on octreotide and did not have a history of diabetes mellitus. Management of the patient's hyperglycemia while receiving parenteral nutrition is described.

Kita‐kyushu lung cancer antigen 1 (KK‐LC‐1) is a kind of cancer‐testis antigen with anti‐tumor potential for clinical application. As a class of small‐molecule antigen conjugate, tumor‐targeting peptides have broad application prospects in gastric cancer diagnosis, imaging, and biological treatment. Here, we screened specific cyclic nonapeptides from a phage‐display library. The targeting peptide with the best affinity was selected and further verified in ex vivo tissue sections. Finally, enrichment of targeting peptides in tumor tissues was observed in vivo, and the dynamic biodistribution process was also observed with micro‐positron emission tomography (micro‐PET)/computed tomography (CT) imaging. Studies showed that the specific cyclic nonapeptide had a high binding capacity for KK‐LC‐1 protein. It has a strong affinity and specificity for KK‐LC‐1‐expressing positive tumor cells. Targeting peptides were significantly enriched at tumor sites in vivo, with very low normal tissue background. These findings demonstrated that the KK‐LC‐1 targeting peptide has high clinical potential., The first publicly reported Kita‐kyushu lung cancer antigen 1 targeting peptide. The peptides showed excellent specificity in PET/CT.

The Ras subfamily of small GTPases is mutated in ∼30% of human cancers and represents compelling yet challenging anticancer drug targets owing to their flat protein surface. We previously reported a bicyclic peptidyl inhibitor, cyclorasin B3, which binds selectively to Ras-GTP with modest affinity and blocks its interaction with downstream effector proteins in vitro but lacks cell permeability or biological activity. In this study, optimization of B3 yielded a potent pan-Ras inhibitor, cyclorasin B4-27, which binds selectively to the GTP-bound forms of wild-type and mutant Ras isoforms (KD = 21 nM for KRasG12V-GppNHp) and is highly cell-permeable and metabolically stable (serum t1/2 > 24 h). B4-27 inhibits Ras signaling in vitro and in vivo by blocking Ras from interacting with downstream effector proteins and induces apoptosis of Ras-mutant cancer cells. When administered systemically (i.v.), B4-27 suppressed tumor growth in two different mouse xenograft models at 1-5 mg/kg of daily doses.