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Probing the role of the conserved residue Glu166 in a class A β‐lactamase using neutron and X‐ray protein crystallography
Author(s) -
Langan Patricia S.,
Sullivan Brendan,
Weiss Kevin L.,
Coates Leighton
Publication year - 2020
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.374
H-Index - 138
ISSN - 2059-7983
DOI - 10.1107/s2059798319016334
Subject(s) - active site , acylation , residue (chemistry) , amino acid , mutant , protein structure , peptide sequence , binding site , molecule , stereochemistry , crystallography , biology , chemistry , enzyme , catalysis , biochemistry , gene , organic chemistry
The amino‐acid sequence of the Toho‐1 β‐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 β‐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‐β‐lactam inhibitors such as the recently developed diazobicyclooctane inhibitor avibactam.