6u58

Publication Abstract from PubMed

The amino-acid sequence of the Toho-1 beta-lactamase contains several conserved residues in the active site, including Ser70, Lys73, Ser130 and Glu166, some of which coordinate a catalytic water molecule. This catalytic water molecule is essential in the acylation and deacylation parts of the reaction mechanism through which Toho-1 inactivates specific antibiotics and provides resistance to its expressing bacterial strains. To investigate the function of Glu166 in the acylation part of the catalytic mechanism, neutron and X-ray crystallographic studies were performed on a Glu166Gln mutant. The structure of this class A beta-lactamase mutant provides several insights into its previously reported reduced drug-binding kinetic rates. A joint refinement of both X-ray and neutron diffraction data was used to study the effects of the Glu166Gln mutation on the active site of Toho-1. This structure reveals that while the Glu166Gln mutation has a somewhat limited impact on the positions of the conserved amino acids within the active site, it displaces the catalytic water molecule from the active site. These subtle changes offer a structural explanation for the previously observed decreases in the binding of non-beta-lactam inhibitors such as the recently developed diazobicyclooctane inhibitor avibactam.

Probing the role of the conserved residue Glu166 in a class A beta-lactamase using neutron and X-ray protein crystallography.,Langan PS, Sullivan B, Weiss KL, Coates L Acta Crystallogr D Struct Biol. 2020 Feb 1;76(Pt 2):118-123. doi:, 10.1107/S2059798319016334. Epub 2020 Jan 24. PMID:32038042^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.