Mapping the phoP transcription starting points. The PE and RPA products were subjected to electrophoresis in 6% (wt/vol) polyacrylamide-8 M urea gels and then to autoradiography. (A) Products of PE analysis using total RNA from M. smegmatis mc2155 (lane 2), M. smegmatis mc2155:pNBV1 (lane 3), M. smegmatis mc2155:pSO5 (lane 4), M. smegmatis mc2155:pSO7 (lane 5) and using no RNA (lane 1). tsp1, tsp1*, and tsp2 are the putative transcription start points of potential phoP promoters for M. tuberculosis (pSO5) and the B strain (pSO7). The tsp1 for the B strain (tsp1*) lies within the IS6110 nucleotide sequence. No phoP transcripts were detected with the control strains (M. smegmatis mc2155 and the same strain transformed with pNBV1). (B) Products of RPA of M. smegmatis mc2155:pSO7 (lane 1) and a probe (lane 2). The locations of the transcription starting points (tsp1* and tsp2) are indicated. (C) Schematic figure showing the locations of tsp1, tsp1*, and tsp2 in the promoter regions of M. tuberculosis (pSO5) and the M. bovis B strain (pSO7).