In:
Antimicrobial Agents and Chemotherapy, American Society for Microbiology, Vol. 60, No. 10 ( 2016-10), p. 5828-5840
Abstract:
β-Lactamase production increasingly threatens the effectiveness of β-lactams, which remain a mainstay of antimicrobial chemotherapy. New activities emerge through both mutation of previously known β-lactamases and mobilization from environmental reservoirs. The spread of metallo-β-lactamases (MBLs) represents a particular challenge because of their typically broad-spectrum activities encompassing carbapenems, in addition to other β-lactam classes. Increasingly, genomic and metagenomic studies have revealed the distribution of putative MBLs in the environment, but in most cases their activity against clinically relevant β-lactams and, hence, the extent to which they can be considered a resistance reservoir remain uncharacterized. Here we characterize the product of one such gene, bla Rm3 , identified through functional metagenomic sampling of an environment with high levels of biocide exposure. bla Rm3 encodes a subclass B3 MBL that, when expressed in a recombinant Escherichia coli strain, is exported to the bacterial periplasm and hydrolyzes clinically used penicillins, cephalosporins, and carbapenems with an efficiency limited by high K m values. An Rm3 crystal structure reveals the MBL superfamily αβ/βα fold, which more closely resembles that in mobilized B3 MBLs (AIM-1 and SMB-1) than other chromosomal enzymes (L1 or FEZ-1). A binuclear zinc site sits in a deep channel that is in part defined by a relatively extended N terminus. Structural comparisons suggest that the steric constraints imposed by the N terminus may limit its affinity for β-lactams. Sequence comparisons identify Rm3-like MBLs in numerous other environmental samples and species. Our data suggest that Rm3-like enzymes represent a distinct group of B3 MBLs with a wide distribution and can be considered an environmental reservoir of determinants of β-lactam resistance.
Type of Medium:
Online Resource
ISSN:
0066-4804
,
1098-6596
DOI:
10.1128/AAC.00750-16
Language:
English
Publisher:
American Society for Microbiology
Publication Date:
2016
detail.hit.zdb_id:
1496156-8
SSG:
12
SSG:
15,3
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