Allosteric cooperation in β-lactam binding to a non-classical transpeptidase

Abstract

L,D-transpeptidase function predominates in atypical 3®3 transpeptide networking of peptidoglycan (PG) layer in Mycobacterium tuberculosis. Prior studies of L,D-transpeptidases have identified only the catalytic site that binds to peptide moiety of the PG substrate or ß-lactam antibiotics. This insight was leveraged to develop mechanism of its activity and inhibition by ß-lactams. Here we report identification of an allosteric site at a distance of 21 Å from the catalytic site that binds the sugar moiety of PG substrates (hereafter referred to as the S-pocket). This site also binds a second ß-lactam molecule and influences binding at the catalytic site. We provide evidence that two ß-lactam molecules bind co-operatively to this enzyme, one non-covalently at the S-pocket and one covalently at the catalytic site. This dual ß-lactam binding phenomenon is previously unknown and is an observation that may offer novel approaches for the structure-based design of new drugs against M. tuberculosis./em>.

The l,d-Transpeptidase LdtAb from Acinetobacter baumannii Is Poorly Inhibited by Carbapenems and Has a Unique Structural Architecture

“…coli, which produces six different LDTs, it was demonstrated that only two of them are responsible for the formation of 3–3 cross-links, while the other four perform cross-linking of the Braun lipoprotein to peptidoglycan and cleavage of these cross-linked species, or catalyze replacement of the terminal d -Ala residue in the donor tetrapeptides with noncanonical amino acids. − LDTs differ from DDTs not only in their catalytic mechanism but also in their structural architecture. Currently, structural information is available for around 70 LDTs, which include both apo enzymes and complexes with their cell wall substrates and β-lactam antibiotics. ,,− …”