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bioRxiv · 10.1101/2025.05.23.655743

Binding mode of isoxazolyl penicillins to a Class-A beta-lactamase at ambient conditions

Gore, G.·Prester, A.·Stetten, D. v.·Bartels, K.·Schulz, E. C.
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Abstract

The predominant resistance mechanism observed in Gram-negative bacteria involves the production of {beta}-lactamases, which catalyse the hydrolysis of {beta}-lactam antibiotics, thereby rendering them ineffective. Although isoxazolyl penicillins are available since the 1970s, there are currently no structures in complex with class-A {beta}-lactamases available. In order to support the rational development of new {beta}-lactamase inhibitors, we have analysed the structure of the clinically relevant {beta}-lactamase CTX-M-14 from Klebsiella pneumoniae near physiolog- ical temperatures. By utilizing serial synchrotron crystallography, we demonstrate the acyl-enzyme intermediates of the catalytically impaired CTX-M-14 mutant E166A in complex with three isoxazolyl penicillins: oxacillin, cloxacillin and dichloxacillin. While the three derivatives differ only by one and two Cl atoms, respectively, they show marked differences in their binding mode.

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Gore, G., Prester, A., Stetten, D. v., Bartels, K., Schulz, E. C.. 2025-05-28. Binding mode of isoxazolyl penicillins to a Class-A beta-lactamase at ambient conditions. https://doi.org/10.1101/2025.05.23.655743

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