5G18

Direct Observation of Active-site Protonation States in a Class A beta lactamase with a monobactam substrate

Summary for 5G18

• Entry DOI: 10.2210/pdb5g18/pdb
• Descriptor: BETA-LACTAMASE CTX-M-97, 2-({[(1Z)-1-(2-amino-1,3-thiazol-4-yl)-2-oxo-2-{[(2S,3S)-1-oxo-3-(sulfoamino)butan-2-yl]amino}ethylidene]amino}oxy)-2-methylpropanoic acid, SULFATE ION, ... (4 entities in total)
• Functional Keywords: hydrolase, beta lactamase, toho, neutron
• Biological source: ESCHERICHIA COLI
• Total number of polymer chains: 1
• Total formula weight: 29035.52

Authors

Vandavasi, V.G.,Weiss, K.L.,Parks, J.M.,Cooper, J.B.,Ginell, S.L.,Coates, L. (deposition date: 2016-03-23, release date: 2016-11-09, Last modification date: 2024-10-16)

Primary citation

Vandavasi, V.G.,Langan, P.S.,Weiss, K.L.,Parks, J.M.,Cooper, J.B.,Ginell, S.L.,Coates, L.
Active-Site Protonation States in an Acyl-Enzyme Intermediate of a Class A beta-Lactamase with a Monobactam Substrate.
Antimicrob. Agents Chemother., 61:-, 2017

PubMed Abstract: 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.

PubMed: 27795378
DOI: 10.1128/AAC.01636-16

Experimental method

X-RAY DIFFRACTION (1.1 Å)