6p56

Publication Abstract from PubMed

Resistance of Neisseria gonorrhoeae to extended-spectrum cephalosporins (ESCs) has become a major threat to human health. The primary mechanism by which N. gonorrhoeae becomes resistant to ESCs is by acquiring a mosaic penA gene, encoding penicillin-binding protein 2 (PBP2) variants. Such variants contain up to 62 mutations compared with wild-type, of which a subset contribute to resistance. To interpret molecular mechanisms underpinning cephalosporin resistance, it is necessary to know how PBP2 is acylated by ESCs. Here, we report the crystal structures of the transpeptidase domain of wild-type PBP2 in complex with cefixime and ceftriaxone, along with structures of PBP2 in apo form and with a phosphate ion bound in the active site at resolutions of 1-7-1.9 A. These structures reveal that acylation of PBP2 by ESCs is accompanied by rotation of the Thr498 sidechain in the KTG motif to contact the cephalosporin carboxylate, twisting of the beta3 strand to form the oxyanion hole, and rolling of the beta3-beta4 loop toward the active site. Recognition of the cephalosporin carboxylate appears to be the key trigger for formation of an acylation-competent state of PBP2. The structures also begin to explain the impact of mutations implicated in ESC resistance. In particular, a G545S mutation may hinder twisting of beta3 because its sidechain hydroxyl forms a hydrogen bond with Thr498. Overall, our data suggest that acylation is initiated by conformational changes elicited or trapped by binding of ESCs and that these movements are restricted by mutations associated with resistance against ESCs.

Recognition of the beta-lactam Carboxylate Triggers Acylation of Neisseria gonorrhoeae Penicillin-Binding Protein 2.,Singh A, Tomberg J, Nicholas RA, Davies C J Biol Chem. 2019 Jul 30. pii: RA119.009942. doi: 10.1074/jbc.RA119.009942. PMID:31362987^[1]

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