title: Structural Characterization and Ligand/Inhibitor Identification Provide Functional Insights into the Mycobacterium tuberculosis Cytochrome P450 CYP126A1.
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.
authors.affiliation: From the Manchester Institute of Biotechnology, School of Chemistry, University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom.
authors.forename: Jude T
authors.initials: JT
authors.lastname: Chenge
authors.affiliation: From the Manchester Institute of Biotechnology, School of Chemistry, University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom.
authors.forename: Le Van
authors.initials: LV
authors.lastname: Duyet
authors.affiliation: From the Manchester Institute of Biotechnology, School of Chemistry, University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom.
authors.forename: Shalini
authors.initials: S
authors.lastname: Swami
authors.affiliation: From the Manchester Institute of Biotechnology, School of Chemistry, University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom.
authors.forename: Kirsty J
authors.initials: KJ
authors.lastname: McLean
authors.affiliation: the Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
authors.forename: Madeline E
authors.initials: ME
authors.lastname: Kavanagh
authors.affiliation: the Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
authors.forename: Anthony G
authors.initials: AG
authors.lastname: Coyne
authors.affiliation: From the Manchester Institute of Biotechnology, School of Chemistry, University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom.
authors.forename: Stephen E J
authors.initials: SE
authors.lastname: Rigby
authors.affiliation: the School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, United Kingdom, and.
authors.forename: Myles R
authors.initials: MR
authors.lastname: Cheesman
authors.affiliation: From the Manchester Institute of Biotechnology, School of Chemistry, University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom.
authors.forename: Hazel M
authors.initials: HM
authors.lastname: Girvan
authors.affiliation: From the Manchester Institute of Biotechnology, School of Chemistry, University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom.
authors.forename: Colin W
authors.initials: CW
authors.lastname: Levy
authors.affiliation: the Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Rupp
authors.affiliation: the Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany.
authors.forename: Jens P
authors.initials: JP
authors.lastname: von Kries
authors.affiliation: the Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
authors.forename: Chris
authors.initials: C
authors.lastname: Abell
authors.affiliation: From the Manchester Institute of Biotechnology, School of Chemistry, University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Leys
authors.affiliation: From the Manchester Institute of Biotechnology, School of Chemistry, University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom, Andrew.Munro@Manchester.ac.uk.
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Munro
mesh_terms: D000935:Antifungal Agents / Q000737:chemistry*; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry*; D020134:Catalytic Domain; D065607:Cytochrome P-450 Enzyme Inhibitors / Q000737:chemistry*; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry* / Q000235:genetics; D007654:Ketoconazole / Q000737:chemistry*; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000235:genetics; D017433:Protein Structure, Secondary
chemical_list: D000935:Antifungal Agents; D001426:Bacterial Proteins; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System; D007654:Ketoconazole
keywords: CYP126A1; Mycobacterium tuberculosis; cytochrome P450; electron paramagnetic resonance (EPR); enzyme structure; high throughput screening (HTS); mass spectrometry (MS); redox potentiometry