MinireviewStructure, function and drug targeting in Mycobacterium tuberculosis cytochrome P450 systems
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)
Microbes Infect.
(2006)Lancet
(2006)- et al.
Curr. Opin. Microbiol.
(2004) - et al.
Cell
(2001) - et al.
Int. J. Antimicrob. Agents
(2006) - et al.
Trends Microbiol.
(2006) - et al.
Biochem. Biophys. Res. Commun.
(2005) - et al.
Genomics
(1996) - et al.
Trends Microbiol.
(2003) - et al.
Structure
(2004)