(A) Intrinsic transcript cleavage property of RNAP.

Stalled elongation complexes bearing the 20 mer transcript were generated with M. smegmatis (Ms), M. tuberculosis (Mtb) and E. coli (Ec) RNAP respectively. The complexes were incubated for a prolonged time (1–4 hrs) in transcription buffer (pH 7.5), followed by resolving the cleavage products on 20% urea-PAGE. (B) pH-induced transcript-cleavage activity of RNAP. The gels show cleaved RNA generated from the 20 mer ternary complexes formed by Ms, Mtb and Ec RNAP in buffers of pH 6.0 to 10.0.