title: Structural analysis of the role of Pseudomonas aeruginosa penicillin-binding protein 5 in β-lactam resistance.
abstract: Penicillin-binding protein 5 (PBP5) is one of the most abundant PBPs in Pseudomonas aeruginosa. Although its main function is that of a cell wall dd-carboxypeptidase, it possesses sufficient β-lactamase activity to contribute to the ability of P. aeruginosa to resist the antibiotic activity of the β-lactams. The study of these dual activities is important for understanding the mechanisms of antibiotic resistance by P. aeruginosa, an important human pathogen, and to the understanding of the evolution of β-lactamase activity from the PBP enzymes. We purified a soluble version of P. aeruginosa PBP5 (designated Pa sPBP5) by deletion of its C-terminal membrane anchor. Under in vitro conditions, Pa sPBP5 demonstrates both dd-carboxypeptidase and expanded-spectrum β-lactamase activities. Its crystal structure at a 2.05-Å resolution shows features closely resembling those of the class A β-lactamases, including a shortened loop spanning residues 74 to 78 near the active site and with respect to the conformations adopted by two active-site residues, Ser101 and Lys203. These features are absent in the related PBP5 of Escherichia coli. A comparison of the two Pa sPBP5 monomers in the asymmetric unit, together with molecular dynamics simulations, revealed an active-site flexibility that may explain its carbapenemase activity, a function that is absent in the E. coli PBP5 enzyme. Our functional and structural characterizations underscore the versatility of this PBP5 in contributing to the β-lactam resistance of P. aeruginosa while highlighting how broader β-lactamase activity may be encoded in the structural folds shared by the PBP and serine β-lactamase classes.
authors: Department of Molecular Medicine, University of South Florida, Tampa, Florida, USA.
authors: Jeffrey D
authors: JD
authors: Smith
authors: Malika
authors: M
authors: Kumarasiri
authors: Weilie
authors: W
authors: Zhang
authors: Dusan
authors: D
authors: Hesek
authors: Mijoon
authors: M
authors: Lee
authors: Marta
authors: M
authors: Toth
authors: Sergei
authors: S
authors: Vakulenko
authors: Jed F
authors: JF
authors: Fisher
authors: Shahriar
authors: S
authors: Mobashery
authors: Yu
authors: Y
authors: Chen
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000378:metabolism; D002268:Carboxypeptidases / Q000737:chemistry* / Q000378:metabolism; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000201:enzymology / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D056004:Molecular Dynamics Simulation; D046915:Penicillin-Binding Proteins / Q000737:chemistry* / Q000235:genetics; D017510:Protein Folding; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000201:enzymology* / Q000378:metabolism; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000737:chemistry* / Q000378:metabolism; D047090:beta-Lactams / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D046915:Penicillin-Binding Proteins; D047090:beta-Lactams; D002268:Carboxypeptidases; D001618:beta-Lactamases; C063912:carbapenemase
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