Download MendeleyProbing the Role of the Conserved Residue Glu166 in a Class A Beta-Lactamase Using Neutron and X-ray Protein Crystallography
Langan, P.S., Sullivan, B., Weiss, K.L., Coates, L.(2020) Acta Crystallogr D Biol Crystallogr 76: 118-123
- PubMed: 32038042
- DOI: https://doi.org/10.1107/S2059798319016334
- Primary Citation of Related Structures:
6U58 - PubMed Abstract:
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.
Organizational Affiliation:
Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
