Understanding the determinants of substrate specificity in IMP family metallo-β-lactamases: the importance of residue 262.


In Gram-negative bacteria, resistance to β-lactam antibacterials is largely due to β-lactamases and is a growing public health threat. One of the most concerning β-lactamases to evolve in bacteria are the Class B enzymes, the metallo-β-lactamases (MBLs). To date, penams and cephems resistant to hydrolysis by MBLs have not yet been found. As a result of this broad substrate specificity, a better understanding of the role of catalytically important amino acids in MBLs is necessary to design novel β-lactams and inhibitors. Two MBLs, the wild type IMP-1 with serine at position 262, and an engineered variant with valine at the same position (IMP-1-S262V), were previously found to exhibit very different substrate spectra. These findings compelled us to investigate the impact of a threonine at position 262 (IMP-1-S262T) on the substrate spectrum. Here, we explore MBL sequence-structure-activity relationships by predicting and experimentally validating the effect of the S262T substitution in IMP-1. Using site-directed mutagenesis, threonine was introduced at position 262, and the IMP-1-S262T enzyme, as well as the other two enzymes IMP-1 and IMP-1-S262V, were purified and kinetic constants were determined against a range of β-lactam antibacterials. Catalytic efficiencies (kcat /KM ) obtained with IMP-1-S262T and minimum inhibitory concentrations (MICs) observed with bacterial cells expressing the protein were intermediate or comparable to the corresponding values with IMP-1 and IMP-1-S262V, validating the role of this residue in catalysis. Our results reveal the important role of IMP residue 262 in β-lactam turnover and support this approach to predict activities of certain novel MBL variants.

Submission Details

ID: qvtjSS8H

Submitter: Peter Oelschlaeger

Submission Date: Aug. 22, 2019, 12:36 p.m.

Version: 1

Publication Details
Pegg KM;Liu EM;George AC;LaCuran AE;Bethel CR;Bonomo RA;Oelschlaeger P,Protein Sci (2014) Understanding the determinants of substrate specificity in IMP family metallo-β-lactamases: the importance of residue 262. PMID:25131397
Additional Information

According to the standard numbering scheme (PMID 15215079) residue 196 is residue 262. ND indicates not detectable. S, I, and R indicate susceptible, intermediate, and resistant, respectively.

Structure view and single mutant data analysis

Study data

No weblogo for data of varying length.
Colors: D E R H K S T N Q A V I L M F Y W C G P

Data Distribution

Studies with similar sequences (approximate matches)

Correlation with other assays (exact sequence matches)

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
100.0 A Metallo-beta-lactamase type 2 P52699 BLAB_SERMA