Pathogenic serotypes of Vibrio cholerae cause the life-threatening diarrheal disease cholera. The increasing development of bacterial resistances against the known antibiotics necessitates the search for new antimicrobial compounds and targets for this pathogen.
Side-chain oligo- and polyglutamylation represents an important posttranslational modification in tubulin physiology. The particular number of glutamate units is related to specific regulatory functions. In this work, we present a method for the synthesis of building blocks for the Fmoc synthesis of peptides containing main chain glutamic acid residues that carry side-chain branching with oligo-glutamic acid. The two model peptide sequences CYEEVGVDSVEGEG-E(E(x))-EEGEEY and CQDATADEQG-E(E(x))-FEEEEGEDEA from the C-termini of mammalian ?1- and ?1-tubulin, respectively, containing oligo-glutamic acid side-chain branching with lengths of 1 to 5 amino acids were assembled in good yield and purity. The products may lead to the generation of specific antibodies which should be important tools for a more detailed investigation of polyglutamylation processes.
In many bacterial species, the translational GTPase TypA acts as a global stress- and virulence regulator and also mediates resistance to the antimicrobial peptide BPI. On the chromosome of M. tuberculosis, typA is located next to narGHJI, which plays a role in adaptation of the pathogen to various environmental conditions. Here, we show that Mycobacterium tuberculosis is sensitive to P2, a derivative of BPI. Using a typA mutant of M. tuberculosis, we found this phenotype to be independent of TypA. We further tested typA expression in M. tuberculosis under defined stress conditions, such as oxygen- and nutrient depletion, low pH, heat shock, antibiotic stress and the presence of P2, and found that typA expression remains unaffected by any of these conditions. Analysis of growth and whole-genome expression revealed similar growth kinetics and gene expression profiles of the wild type and the mutant under normal growth conditions as well as under stress conditions. Our results suggest that in contrast to the findings in other bacteria, TypA does not act as a global stress- and virulence regulator in M. tuberculosis.
The cGMP-dependent protein kinase type I (PKG I) is an essential regulator of cellular function in blood vessels throughout the body. DT-2, a peptidic inhibitor of PKG, has played a central role in determining the molecular mechanisms of vascular control involving PKG and its signaling partners. Here, we report the development of (d)-amino acid DT-2 derivatives, namely the retro-inverso ri-(d)-DT-2 and the all (d)-amino acid analog, (d)-DT-2. Both peptide analogs were potent PKG Ialpha inhibitors with K(i) values of 5.5 nM (ri-(d)-DT-2) and 0.8 nM ((d)-DT-2) as determined using a hyperbolic mixed-type inhibition model. Also, both analogs were proteolytically stable in vivo, showed elevated selectivity, and displayed enhanced membrane translocation properties. Studies on isolated arteries from the resistance vasculature demonstrated that intraluminally perfused (d)-DT-2 significantly inhibited vasodilation induced by 8-Br-cGMP. Furthermore, in vivo application of (d)-DT-2 established a uniform translocation pattern in the resistance vasculature, with exception of the brain. Thus, (d)-DT-2 caused significant increases in mean arterial blood pressure in unrestrained, awake mice. Further, mesenteric arteries isolated from (d)-DT-2 treated animals showed a markedly reduced dilator response to 8-Br-cGMP in vitro. Our results clearly demonstrate that (d)-DT-2 is a superior inhibitor of PKG Ialpha and its application in vivo leads to sustained inhibition of PKG in vascular smooth muscle cells. The discovery of (d)-DT-2 may help our understanding of how blood vessels constrict and dilate and may also aid the development of new strategies and therapeutic agents targeted to the prevention and treatment of vascular disorders such as hypertension, stroke and coronary artery disease.
Naturally occurring antimicrobial peptides contain a large number of amino acid residues, which limits their clinical applicability. In search of short antimicrobial peptides, which represent a possible alternative for lead structures to fight antibiotic resistant microbial infections, a series of synthetic peptide analogues based on Trp-His and His-Arg structural frameworks have been prepared and found to be active against several Gram-negative and Gram-positive bacterial strains as well as against a fungal strain with MIC values of the most potent structures in the range of 5-20 microg/mL ((IC(50) in the range of 1-5 microg/mL). The synthesized peptides showed no cytotoxic effect in an MTT assay up to the highest test concentration of 200 microg/mL. A combination of small size, presence of unnatural amino acids, high antimicrobial activity, and absence of cytotoxicity reveals the synthesized Trp-His and His-Arg analogues as promising candidates for novel antimicrobial therapeutics.
There is an urgent need for new drugs against influenza type A and B viruses due to incomplete protection by vaccines and the emergence of resistance to current antivirals. The influenza virus polymerase complex, consisting of the PB1, PB2 and PA subunits, represents a promising target for the development of new drugs. We have previously demonstrated the feasibility of targeting the protein-protein interaction domain between the PB1 and PA subunits of the polymerase complex of influenza A virus using a small peptide derived from the PA-binding domain of PB1. However, this influenza A virus-derived peptide did not affect influenza B virus polymerase activity. Here we report that the PA-binding domain of the polymerase subunit PB1 of influenza A and B viruses is highly conserved and that mutual amino acid exchange shows that they cannot be functionally exchanged with each other. Based on phylogenetic analysis and a novel biochemical ELISA-based screening approach, we were able to identify an influenza A-derived peptide with a single influenza B-specific amino acid substitution which efficiently binds to PA of both virus types. This dual-binding peptide blocked the viral polymerase activity and growth of both virus types. Our findings provide proof of principle that protein-protein interaction inhibitors can be generated against influenza A and B viruses. Furthermore, this dual-binding peptide, combined with our novel screening method, is a promising platform to identify new antiviral lead compounds.
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