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    Active-site protonation states in an Acyl-Enzyme intermediate of a Class A β-Lactamase with a Monobactam Substrate

    Vandavasi, V.G. and Langan, P.S. and Weiss, K.L. and Parks, J.M. and Cooper, Jonathan B. and Ginell, S.L. and Coates, L. (2016) Active-site protonation states in an Acyl-Enzyme intermediate of a Class A β-Lactamase with a Monobactam Substrate. Antimicrobial Agents and Chemotherapy 61 (1), e01636-16. ISSN 0066-4804.

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    The monobactam antibiotic aztreonam is used to treat cystic fibrosis patients with chronic pulmonary infections colonized by Pseudomonas aeruginosa strains expressing CTX-M extended-spectrum β-lactamases. The protonation states of active-site residues that are responsible for hydrolysis have been determined previously for the apo form of a CTX-M β-lactamase but not for a monobactam acyl-enzyme intermediate. Here we used neutron and high-resolution X-ray crystallography to probe the mechanism by which CTX-M extended-spectrum β-lactamases hydrolyze monobactam antibiotics. In these first reported structures of a class A β-lactamase in an acyl-enzyme complex with aztreonam, we directly observed most of the hydrogen atoms (as deuterium) within the active site. Although Lys 234 is fully protonated in the acyl intermediate, we found that Lys 73 is neutral. These findings are consistent with Lys 73 being able to serve as a general base during the acylation part of the catalytic mechanism, as previously proposed.


    Item Type: Article
    Keyword(s) / Subject(s): β-lactamase, aztreonam, acyl-enzyme complex, neutron structure, X-ray structure
    School: Birkbeck Faculties and Schools > Faculty of Science > School of Natural Sciences
    Depositing User: Administrator
    Date Deposited: 01 Jun 2017 08:45
    Last Modified: 02 Aug 2023 17:33


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