7QQC

Structure of CTX-M-15 K73A mutant

Summary for 7QQC

• Entry DOI: 10.2210/pdb7qqc/pdb
• Descriptor: Beta-lactamase, SULFATE ION, CHLORIDE ION, ... (4 entities in total)
• Functional Keywords: beta-lactamase, mutant, antibiotic resistance, antimicrobial protein
• Biological source: Klebsiella pneumoniae IS53
• Total number of polymer chains: 1
• Total formula weight: 28654.59

Authors

Tooke, C.L.,Hinchliffe, P.,Spencer, J. (deposition date: 2022-01-07, release date: 2022-05-25, Last modification date: 2024-01-31)

Primary citation

Hinchliffe, P.,Tooke, C.L.,Bethel, C.R.,Wang, B.,Arthur, C.,Heesom, K.J.,Shapiro, S.,Schlatzer, D.M.,Papp-Wallace, K.M.,Bonomo, R.A.,Spencer, J.
Penicillanic Acid Sulfones Inactivate the Extended-Spectrum beta-Lactamase CTX-M-15 through Formation of a Serine-Lysine Cross-Link: an Alternative Mechanism of beta-Lactamase Inhibition.
Mbio, 13:e0179321-e0179321, 2022

PubMed Abstract: β-Lactamases hydrolyze β-lactam antibiotics and are major determinants of antibiotic resistance in Gram-negative pathogens. Enmetazobactam (formerly AAI101) and tazobactam are penicillanic acid sulfone (PAS) β-lactamase inhibitors that differ by an additional methyl group on the triazole ring of enmetazobactam, rendering it zwitterionic. In this study, ultrahigh-resolution X-ray crystal structures and mass spectrometry revealed the mechanism of PAS inhibition of CTX-M-15, an extended-spectrum β-lactamase (ESBL) globally disseminated among . CTX-M-15 crystals grown in the presence of enmetazobactam or tazobactam revealed loss of the Ser70 hydroxyl group and formation of a lysinoalanine cross-link between Lys73 and Ser70, two residues critical for catalysis. Moreover, the residue at position 70 undergoes epimerization, resulting in formation of a d-amino acid. Cocrystallization of enmetazobactam or tazobactam with CTX-M-15 with a Glu166Gln mutant revealed the same cross-link, indicating that this modification is not dependent on Glu166-catalyzed deacylation of the PAS-acylenzyme. A cocrystal structure of enmetazobactam with CTX-M-15 with a Lys73Ala mutation indicates that epimerization can occur without cross-link formation and positions the Ser70 Cβ closer to Lys73, likely facilitating formation of the Ser70-Lys73 cross-link. A crystal structure of a tazobactam-derived imine intermediate covalently linked to Ser70, obtained after 30 min of exposure of CTX-M-15 crystals to tazobactam, supports formation of an initial acylenzyme by PAS inhibitors on reaction with CTX-M-15. These data rationalize earlier results showing CTX-M-15 deactivation by PAS inhibitors to involve loss of protein mass, and they identify a distinct mechanism of β-lactamase inhibition by these agents. β-Lactams are the most prescribed antibiotic class for treating bacterial diseases, but their continued efficacy is threatened by bacterial strains producing β-lactamase enzymes that catalyze their inactivation. The CTX-M family of ESBLs are major contributors to β-lactam resistance in , preventing effective treatment with most penicillins and cephalosporins. Combining β-lactams with β-lactamase inhibitors (BLIs) is a validated route to overcome such resistance. Here, we describe how exposure to enmetazobactam and tazobactam, BLIs based on a penicillanic acid sulfone (PAS) scaffold, leads to a protein modification in CTX-M-15, resulting in irremediable inactivation of this most commonly encountered member of the CTX-M family. High-resolution X-ray crystal structures showed that PAS exposure induces formation of a cross-link between Ser70 and Lys73, two residues critical to β-lactamase function. This previously undescribed mechanism of inhibition furthers our understanding of β-lactamase inhibition by classical PAS inhibitors and provides a basis for further, rational inhibitor development.

PubMed: 35612361
DOI: 10.1128/mbio.01793-21

Experimental method

X-RAY DIFFRACTION (0.95 Å)