Solution NMR Studies of CYP121 of <i>Mycobacterium tuberculosis</i> ; Evidence that Ligand Binding is Bi‐modal

Mycobacterium tuberculosis (Mtb) is the causative pathogen in the development of tuberculosis (TB). The rise of multi‐drug resistant forms of TB, combined with the fact that one third of the world’s population are carriers of latent TB, underscores the need for the development of novel anti‐TB agents. A current drug target is the cytochrome P450 (CYP) 121 of Mtb; an essential enzyme that mediates an unusual phenol coupling reaction of the dipeptide di‐cyclotyrosine (cYY). Our current understanding of atomic level active site/inhibitor interactions in CYP121 stems primarily from co‐crystallization of drug fragments or cYY with the enzyme. However, these studies result in protein structures that reflect the same unchanging conformation, thus resulting in a gap in our understanding of dynamic active site/ligand interactions that would otherwise help inform specificity in the design of novel CYP121 inhibitors. In this preliminary work, we’ve begun to address this gap by adapting CYP121 for analysis by solution NMR. The enzyme produces a well‐dispersed, resolvable 1H‐15N HSQC spectrum. We have acquired 2D spectra of the enzyme while bound to a variety of azoles representing a range of ligand sizes and chemistry. We report that, while ligands with a similar overall structure (econazole and miconazole) produce similar perturbations of the NMR spectra, other ligands with distinct overall structures (ketoconazole and fluconazole) produce chemical shift perturbations that are unexpectedly similar to each other, yet can be categorized separately from other ligand‐induced changes. These preliminary studies suggest that ligand binding in CYP121 is partially bi‐modal, indicative of a structure that retains a semi‐rigid backbone in solution. This work lays the foundation for understanding CYP121 dynamics that will be a critical component of future drug design of novel anti‐TB agents. Support or Funding Information Research supported by start‐up funds at SUNY Buffalo A backbone amide resonance of CYP121 in response to azole binding Figure 1