FIG. 5.

KCl dependence of the leuV promoter transcription in vitro. (A) Single round of transcription. Supercoiled plasmid templates containing either the wild-type leuV promoter (filled circles) or the D mutant promoter (open circles) were preincubated with RNA polymerase at different concentrations of KCl. Reactions were initiated by the addition of all NTPs and heparin as indicated in Materials and Methods. Templates employed for transcription contained leuV operon sequences from positions −50 to +67 inserted into pLTC76 (see Materials and Methods), producing 132-nucleotide transcripts. (B) Multiple rounds of transcription. Transcription was initiated by the addition of RNA polymerase to supercoiled plasmid templates described above containing either the wild type (filled circles) or the D mutant (open circles). The activities of these templates at increasing concentrations of KCl are indicated.