Azole-antifungal binding to a novel cytochrome P450 from Mycobacterium tuberculosis:: implications for treatment of tuberculosis

Although antibiotics against Mycobacterium tuberculosis have decreased the incidence of tuberculosis infections significantly, the emergence of drug-resistant strains of this deadly pathogen renders current treatments ineffective. Therefore, it is imperative to identify biochemical pathways in M. tuberculosis that can serve as targets for new anti-mycobacterial drugs. We recently cloned, expressed, and purified MT CYP51, a soluble protein from M. tuberculosis that is similar in sequence to CYP51 (lanosterol-14 alpha -demethylase) isozymes, pharmacological targets for several anti-mycotic compounds. Its striking amino acid sequence similarity to that of mammalian and fungal CYP51s led to the hypothesis that MT CYP51 plays an important role in mycobacterial biology that can be targeted for drug action. In this manuscript, we established through spectral analysis that several azole antifungals bind MT CYP51 with high affinity. The effects of several azole compounds on the growth of M. bovis and M, smegmatis, two mycobacterial species that closely resemble M. tuberculosis were examined. We established a correlation between the affinity of azole compounds to MT CYP51 and their ability to impair the growth of M. bovis and M. smegmatis. These results suggest that the metabolic functions of MT CYP51 may be comparable to those of CYP51 in yeast and fungi and may lead to the development of a new generation of anti-mycobacterial agents. (C) 2001 Elsevier Science Inc. All rights reserved.