6cac

Publication Abstract from PubMed

Carbapenems are "last resort" beta-lactam antibiotics used to treat serious and life-threatening health care-associated infections caused by multidrug-resistant Gram-negative bacteria. Unfortunately, the worldwide spread of genes coding for carbapenemases among these bacteria is threatening these life-saving drugs. Metallo-beta-lactamases (MbetaLs) are the largest family of carbapenemases. These are Zn(II)-dependent hydrolases that are active against almost all beta-lactam antibiotics. Their catalytic mechanism and the features driving substrate specificity have been matter of intense debate. The active sites of MbetaLs are flanked by two loops, one of which, loop L3, was shown to adopt different conformations upon substrate or inhibitor binding, and thus are expected to play a role in substrate recognition. However, the sequence heterogeneity observed in this loop in different MbetaLs has limited the generalizations about its role. Here, we report the engineering of different loops within the scaffold of the clinically relevant carbapenemase NDM-1. We found that the loop sequence dictates its conformation in the unbound form of the enzyme, eliciting different degrees of active-site exposure. However, these structural changes have a minor impact on the substrate profile. Instead, we report that the loop conformation determines the protonation rate of key reaction intermediates accumulated during the hydrolysis of different beta-lactams in all MbetaLs. This study demonstrates the existence of a direct link between the conformation of this loop and the mechanistic features of the enzyme, bringing to light an unexplored function of active-site loops on MbetaLs.

The Reaction Mechanism of Metallo-beta-Lactamases Is Tuned by the Conformation of an Active-Site Mobile Loop.,Palacios AR, Mojica MF, Giannini E, Taracila MA, Bethel CR, Alzari PM, Otero LH, Klinke S, Llarrull LI, Bonomo RA, Vila AJ Antimicrob Agents Chemother. 2018 Dec 21;63(1). pii: AAC.01754-18. doi:, 10.1128/AAC.01754-18. Print 2019 Jan. PMID:30348667^[1]

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