19F-NMR monitoring of reversible protein post-translational modifications: class D β-lactamase carbamylation and inhibition

Bacterial production of β-lactamases with carbapenemase activity is a global health threat. The active sites of class D carbapenemases such as OXA-48, which is of major clinical importance, uniquely contain a carbamylated lysine residue which is essential for catalysis. Although there is significant interest in characterizing this post-translational modification, and it is a promising inhibition target, protein carbamylation is challenging to monitor in solution. We report the use of 19F-NMR spectroscopy to monitor the carbamylation state of 19F-labelled OXA-48. This method was used to investigate the interactions of OXA-48 with clinically used serine βlactamase inhibitors, including avibactam and vaborbactam. Crystallographic studies on 19F-labelled OXA-48 provide a structural rationale for the sensitivity of the 19F-label to active site interactions. The overall results demonstrate the use of 19F-NMR to monitor reversible covalent post-translational modifications.