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Structure, function and drug targeting in Mycobacterium tuberculosis cytochrome P450 systems

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Abstract

The human pathogen Mycobacterium tuberculosis has made a dramatic resurgence in recent years. Drug resistant and multidrug resistant strains are prevalent, and novel antibiotic strategies are desperately needed to counter Mtb’s global spread. The M. tuberculosis genome sequence revealed an unexpectedly high number of cytochrome P450 (P450) enzymes (20), and parallel studies indicated that P450-inhibiting azole drugs had potent anti-mycobacterial activity. This article reviews current knowledge of structure/function of P450s and redox partner systems in M. tuberculosis. Recent research has highlighted potential drug target Mtb P450s and provided evidence for roles of selected P450 isoforms in host lipid and sterol/steroid transformations. Structural analysis of key Mtb P450s has provided fundamental information on the nature of the heme binding site, P450 interactions with azole drugs, the biochemical nature of cytochrome P420, and novel mutational adaptations by which azole binding to P450s may be diminished to facilitate azole resistance.

Section snippets

The Mtb genome sequence—a plethora of P450s

The Mtb gene sequence was first determined in the laboratory of Stewart Cole at the Institut Pasteur in 1998, and revealed some unusual phenomena [14]. The large proportion of genes involved in lipid metabolism was not unexpected, given the complexity of lipids in Mtb. The bacterium has a dense, lipid-rich cell envelope that is critical for infection and for persistence in the host (Fig. 2). Of particular note in this envelope are the abundant mycolipids, which are very long chain (C60–C90)

Mtb CYP51—revelations from structural and mechanistic analysis

The presence of a bacterial isoform of the CYP51 family was unexpected, and the fact that the Mtb CYP51 (unlike the eukaryotic CYP51 enzymes) is devoid of a N-terminal membrane anchor region also indicated that the enzyme could be suitable for crystallization and structural analysis in its native form. Early studies on the enzyme indicated it was a bona fide CYP51 with respect to its ability to catalyse 14α-demethylation of lanosterol, 24,25-dihydrolanosterol and the plant sterol obtusifoliol,

CYP121—novel azole binding modes and high resolution structural details

To date, the only other Mtb P450 to be structurally characterized is CYP121, an isoform showing similarities to certain polyketide metabolising P450 isoforms [45]. The amino acid sequence of CYP121 is not sufficiently similar to other P450s in the databases to enable any definitive assignment of substrate class recognized. However, early studies showed that the CYP121 gene could be expressed readily in E. coli, and that the purified CYP121 bound very tightly to a range of azole antifungal

Other P450 systems in Mycobacterium tuberculosis

While far more research efforts have been devoted toward characterization of the Mtb CYP51 and CYP121 P450s, data from various sources (including genetic studies and gene array analyses) have accumulated, pointing to the importance of a number of the other P450s in e.g. Mtb viability and pathogenicity. An immediate observation from analysis of the genome sequences of Mtb and the vaccine strain M. bovis BCG is that two of the P450 genes in Mtb reside in RD regions (Regions of Difference) that

P450 redox partner systems in Mycobacterium tuberculosis

The “typical” prokaryotic P450 enzyme requires communication with a redox system involving two other proteins. These are typically either a ferredoxin (containing an iron sulfur cluster) or a flavodoxin (containing FMN), and a FAD-binding ferredoxin/flavodoxin reductase that sources electrons from NAD(P)H. The prototype is the P450cam system comprising the NADH-specific putidaredoxin reductase and the 2Fe–2S-containing putidaredoxin [59]. While more exotic systems that exploit e.g. enzyme

The relevance of P450 systems as Mtb drug targets—conclusions and future prospects

The revelation that Mtb encodes 20 distinct P450 enzymes led to a major change in the perception in the P450 field regarding the relevance of P450 chemistry to bacterial physiology. The proportion of Mtb’s 4.4 million base pair genome given over to CYP genes is substantially greater than in most eukaryotes (1 P450/220,000 base pairs of the genome), and this is highly suggestive that the Mtb P450s have pivotal roles in physiology and/or viability of the pathogen in its host. For example, humans

Acknowledgments

The authors thank the UK Biotechnology and Biological Sciences Research Council (BBSRC) and the European Union (Framework V programme X-TB and Framework VI programme NM4TB) for funding our research in this area. AWM thanks the Royal Society and Leverhulme Trust (UK) for a Fellowship award. The authors would like to take this opportunity to congratulate Professor Fred Guengerich on his phenomenal contributions over more than 30 years to the detailed understanding of the structure and mechanism

References (84)

  • C. Gradmann

    Microbes Infect.

    (2006)
  • C. Dye

    Lancet

    (2006)
  • K. Duncan et al.

    Curr. Opin. Microbiol.

    (2004)
  • E.A. Campbell et al.

    Cell

    (2001)
  • S. Obata et al.

    Int. J. Antimicrob. Agents

    (2006)
  • K.J. McLean et al.

    Trends Microbiol.

    (2006)
  • M.R. Waterman et al.

    Biochem. Biophys. Res. Commun.

    (2005)
  • D. Rozman et al.

    Genomics

    (1996)
  • F.C. Odds et al.

    Trends Microbiol.

    (2003)
  • L.M. Podust et al.

    Structure

    (2004)
  • A.W. Munro et al.

    Biochim. Biophys. Acta

    (2007)
  • H.M. Girvan et al.

    J. Biol. Chem.

    (2004)
  • A. Bellamine et al.

    J. Lipid Res.

    (2004)
  • G.I. Lepesheva et al.

    J. Biol. Chem.

    (2001)
  • K.J. McLean et al.

    J. Inorg. Biochem.

    (2002)
  • D. Leys et al.

    J. Biol. Chem.

    (2003)
  • F.W. Muskett et al.

    J. Mol. Biol.

    (1996)
  • S. Nagano et al.

    J. Biol. Chem.

    (2005)
  • H.E. Seward et al.

    J. Biol. Chem.

    (2006)
  • P. Brodin et al.

    Trends Microbiol.

    (2004)
  • S.L. Kendall et al.

    Trends Microbiol.

    (2004)
  • C. Recchi et al.

    J. Biol. Chem.

    (2003)
  • T.L. Poulos

    Biochem. Biophys. Res. Commun.

    (2005)
  • G.A. Ziegler et al.

    J. Mol. Biol.

    (1999)
  • J. Li et al.

    J. Biol. Chem.

    (2001)
  • A. Zanno et al.

    Biochim. Biophys. Acta

    (2005)
  • Z. Ahmad et al.

    FEMS Microbiol. Lett.

    (2005)
  • D.R. Nelson

    Arch. Biochem. Biophys.

    (1999)
  • J. Gamieldien et al.

    Trends Genet.

    (2002)
  • T.A. Vannelli et al.

    J. Biol. Chem.

    (2002)
  • D.G. Russell

    Nat. Rev. Microbiol.

    (2007)
  • A.D. Harries et al.

    Annu. Trop. Med. Parasitol.

    (2006)
  • G.S. Timmins et al.

    Molec. Microbiol.

    (2006)
  • X.B. Zhao et al.

    Biochemistry

    (2006)
  • Z. Ying

    Annu. Rev. Pharmacol. Toxicol.

    (2005)
  • R. Johnson et al.

    Curr. Issues Mol. Biol.

    (2006)
  • WHO, http://www.who.int/mediacentre/news/notes/2006/np23/en/index.html,...
  • WHO, http://www.who.int/mediacentre/factsheets/fs104/en/index.html, Fact sheet No. 104,...
  • S.T. Cole et al.

    Nature

    (1998)
  • B.J. Berger et al.

    BMC Microbiol.

    (2003)
  • S.D. Bentley et al.

    Nature

    (2002)
  • R.D. Fleischmann, R.J. Dodson, D.H. Haft, J.S. Merkel, W.C. Nelson, C.M. Fraser,...
  • Cited by (0)

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