FIG 4.

Study of M. tuberculosis complex strains reveals a point mutation in the whiB6 promoter exclusive of the H37Rv strain. (A) The whiB6 gene and flanking sequences were aligned with 100 available mycobacterial genomes. The image shows a single nucleotide insertion (labeled as a G in boldface) upstream of the whiB6 gene exclusively present in H37Rv/Ra, being absent in other M. tuberculosis complex strains. Note the presence of inverted repeats (depicted by arrows) that originated as a consequence of the guanine insertion in H37Rv. (B) Immunoprecipitation of M. tuberculosis DNA with anti-PhoP antibodies and subsequent qRT-PCR quantification of the region adjacent to the G-insertion in the whiB6 promoter. The results show an enrichment of immunoprecipitated DNA in the MT103 and H37Rv WT strains relative to their phoP mutants, indicative of PhoP binding to the whiB6 promoter. (C) Inverted repeats in panel A probably result in formation of the indicated stem-loop structure.