Search

Undecaprenyl pyrophosphate (UPP) is an important carrier of the oligosaccharide component in peptidoglycan synthesis. Inhibition of UPP synthase (UPPS) may be an effective strategy in combating the pathogen Acinetobacter baumannii, which has evolved to be multidrug‐resistant. Here, A. baumannii UPPS (AbUPPS) was cloned, expressed, purified and crystallized, and its structure was determined by X‐ray diffraction. Each chain of the dimeric protein folds into a central β‐sheet with several surrounding α‐helices, including one at the C‐terminus. In the active site, two molecules of citrate interact with the side chains of the catalytic aspartate and serine. These observations may provide a structural basis for inhibitor design against AbUPPS. The inhibition of undecaprenyl pyrophosphate synthase (UPPS) may be an effective strategy in combating the multidrug‐resistant pathogen Acinetobacter baumannii. The structure of UPPS from A. baumannii reported here may provide a structural basis for inhibitor design. [ABSTRACT FROM AUTHOR]

Abstract: We report the first X‐ray crystallographic structure of the “head‐to‐middle” prenyltransferase, isosesquilavandulyl diphosphate synthase, involved in biosynthesis of the merochlorin class of antibiotics. The protein adopts the ζ or cis‐prenyl transferase fold but remarkably, unlike tuberculosinol adenosine synthase and other cis‐prenyl transferases (e.g. cis‐farnesyl, decaprenyl, undecaprenyl diphosphate synthases), the large, hydrophobic side chain does not occupy a central hydrophobic tunnel. Instead, it occupies a surface pocket oriented at 90° to the hydrophobic tunnel. Product chain‐length control is achieved by squeezing out the ligand from the conventional allylic S1 binding site, with proton abstraction being achieved using a diphosphate‐Asn‐Ser relay. The structures revise and unify our thinking as to the mechanism of action of many other prenyl transferases and may also be of use in engineering new merochlorin‐class antibiotics. [ABSTRACT FROM AUTHOR]

Staphylococci cause a wide range of diseases in humans and animals, and the proteins of the multiple antibiotic-resistance repressor (MarR) family in staphylococci function as regulators of protein expression and confer resistance to multiple antibiotics. Diverse mechanisms such as biofilm formation, drug transport, drug modification etc. are associated with this resistance. In this study, crystal structures of the Staphylococcus aureus MarR homologue SAR2349 and its complex with salicylate and the aminoglycoside antibiotic kanamycin have been determined. The structure of SAR2349 shows for the first time that a MarR protein can interact directly with different classes of ligands simultaneously and highlights the importance and versatility of regulatory systems in bacterial antibiotic resistance. The three-dimensional structures of TcaR from S. epidermidis in complexes with chloramphenicol and with the aminoglycoside antibiotic streptomycin were also investigated. The crystal structures of the TcaR and SAR2349 complexes illustrate a general antibiotic-regulated resistance mechanism that may extend to other MarR proteins. To reveal the regulatory mechanism of the MarR proteins, the protein structures of this family were further compared and three possible mechanisms of regulation are proposed. These results are of general interest because they reveal a remarkably broad spectrum of ligand-binding modes of the multifunctional MarR proteins. This finding provides further understanding of antimicrobial resistance mechanisms in pathogens and strategies to develop new therapies against pathogens. [ABSTRACT FROM AUTHOR]

Streptosporangium sibiricum SibL catalyzes the methyl transfer from S-adenosylmethionine (SAM) to 3-hydroxykynurenine (3-HK) to produce S-adenosylhomocysteine (SAH) and 3-hydroxy-4-methyl-kynurenine for sibiromycin biosynthesis. Here, we present the crystal structures of apo-form Ss-SibL, Ss-SibL/SAH binary complex and Ss-SibL/SAH/3-HK ternary complex. Ss-SibL is a homodimer. Each subunit comprises a helical N-terminal domain and a Rossmann-fold C-terminal domain. SAM (or SAH) binding alone results in domain movements, suggesting a two-step catalytic cycle. Analyses of the enzyme-ligand interactions and further mutant studies support a mechanism in which Tyr134 serves as the principal base in the transferase reaction of methyl group from SAM to 3-HK. [ABSTRACT FROM AUTHOR]

Wereport the results of an investigation of the activity of aseries of amidine and bisamidine compounds against Staphylococcus aureusand Escherichiacoli. The most active compounds bound to an AT-richDNA dodecamer (CGCGAATTCGCG)2and using DSC were foundto increase the melting transition by up to 24 °C. Several compoundsalso inhibited undecaprenyl diphosphate synthase (UPPS) with IC50values of 100–500 nM, and we found good correlations(R2= 0.89, S. aureus; R2= 0.79, E. coli) between experimental and predicted cell growth inhibition by usingDNA ΔTmand UPPS IC50experimental results together with one computed descriptor. We alsosolved the structures of three bisamidines binding to DNA as wellas three UPPS structures. Overall, the results are of general interestin the context of the development of resistance-resistant antibioticsthat involve multitargeting. [ABSTRACT FROM AUTHOR]