[Genetic heterogeneity of cytochrome CYP51 in clinical strains of Mycobacterium tuberculosis].

Information on the complete genome sequences of a number of organisms available recently offers essentially new opportunities for the development of new, highly effective antimicrobial compounds. In particular, the search for new effective antituberculosis drugs remains an important problem, due to the recent increase of number of patients suffering with tuberculosis. In this respect considerable attention is paid to the cyp51-like gene Rv0764c encoding sterol-14 alpha-demethylase belonging to the cytochrome P450 superfamily, which has been discovered by computer analysis of the Mycobacterium tuberculosis genome sequence. We have screened 64 clinical isolates of M. tuberculosis for functionally relevant mutations in the coding sequence of the gene encoding Cyp 51-demethylase by single-strand conformation polymorphism analysis (SSCP) and sequencing of PCR-amplified gene fragments. Structural analysis of the gene in the isolates revealed no mutations leading to amino acid substitutions in the corresponding protein. 10 isolates had a silent nucleotide substitution 114 GCT-->GCC. Computer analysis of cyp51 sequence of the CDC1551 strain also revealed a similar nucleotide substitution, which has not been mentioned previously. The data obtained demonstrate that the sequence of the gene is highly conserved, supporting the advisability of M. tuberculosis Cyp51 protein to be considered as a molecular target for new antitubercular drugs. The SNP found in the gene coding sequence may be employed in the studies of M. tuberculosis population genetics.