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Structural characterization and ligand/inhibitor identification provide functional insights into the mycobacterium tuberculosis cytochrome P450 CYP126A1

Item Type:Article
Title:Structural characterization and ligand/inhibitor identification provide functional insights into the mycobacterium tuberculosis cytochrome P450 CYP126A1
Creators Name:Chenge, J.T. and Duyet, L.V. and Swami, S. and McLean, K.J. and Kavanagh, M.E. and Coyne, A.G. and Rigby, S.E.J. and Cheesman, M.R. and Girvan, H.M. and Levy, C.W. and Rupp, B. and von Kries, J.P. and Abell, C. and Leys, D. and Munro, A.W.
Abstract:The Mycobacterium tuberculosis H37Rv genome encodes 20 cytochromes P450, including P450s crucial to infection and bacterial viability. Many M. tuberculosis P450s remain uncharacterized, suggesting that their further analysis may provide new insights into M. tuberculosis metabolic processes and new targets for drug discovery. CYP126A1 is representative of a P450 family widely distributed in mycobacteria and other bacteria. Here we explore the biochemical and structural properties of CYP126A1, including its interactions with new chemical ligands. A survey of azole antifungal drugs showed that CYP126A1 is inhibited strongly by azoles containing an imidazole ring but not by those tested containing a triazole ring. To further explore the molecular preferences of CYP126A1 and search for probes of enzyme function, we conducted a high throughput screen. Compounds containing three or more ring structures dominated the screening hits, including nitroaromatic compounds that induce substrate-like shifts in the heme spectrum of CYP126A1. Spectroelectrochemical measurements revealed a 155-mV increase in heme iron potential when bound to one of the newly identified nitroaromatic drugs. CYP126A1 dimers were observed in crystal structures of ligand-free CYP126A1 and for CYP126A1 bound to compounds discovered in the screen. However, ketoconazole binds in an orientation that disrupts the BC-loop regions at the P450 dimer interface and results in a CYP126A1 monomeric crystal form. Structural data also reveal that nitroaromatic ligands "moonlight" as substrates by displacing the CYP126A1 distal water but inhibit enzyme activity. The relatively polar active site of CYP126A1 distinguishes it from its most closely related sterol-binding P450s in M. tuberculosis, suggesting that further investigations will reveal its diverse substrate selectivity.
Keywords:Antifungal Agents, Bacterial Proteins, Catalytic Domain, Cytochrome P-450 Enzyme Inhibitors, Cytochrome P-450 Enzyme System, Ketoconazole, Mycobacterium tuberculosis, Secondary Protein Structure
Source:Journal of Biological Chemistry
Publisher:American Society for Biochemistry and Molecular Biology
Page Range:1310-1329
Date:27 January 2017
Official Publication:https://doi.org/10.1074/jbc.M116.748822
PubMed:View item in PubMed

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