CHARACTERIZATION OF MYCOBACTERIUM-TUBERCULOSIS LEXA - RECOGNITION OF A CHEO (BACILLUS-TYPE SOS) BOX

The gene coding for the Mycobacterium tuberculosis homologue of LexA h as been cloned and sequenced. Amino acids required for autocatalytic c leavage are conserved, whereas those important for specific DNA bindin g are not, when compared with Escherichia coli LexA. The transcription al start site was mapped and a DNA sequence motif was identified which resembled the consensus Cheo box sequence involved in the regulation of DNA-damage-inducible genes in Bacillus subtilis. The M. tuberculosi s LexA protein was overexpressed in E. coli and purified by means of a His tag. The purifed LexA was shown to bind to the Cheo box sequence found upstream of its own gene.