Promoter recognition by sigma-37 RNA polymerase from Bacillus subtilis

Bacillus subtilis possesses at least five different forms of RNA polymerase holoenzyme which are distinguished by their sigma subunit and their promoter recognition specificity. Sigma-37 RNA polymerase, a minor form of RNA polymerase, recognizes a class of promoters, which includes promoters for genes transcribed early during endospore formation. We have used site-directed bisulfite mutagenesis to construct a series of single and multiple base substitutions in a promoter recognized by sigma-37 RNA polymerase. In vitro transcription analysis of this series of mutant promoters demonstrated that single base substitutions at positions -36, -16, -15 and -14 most dramatically reduced the efficiency of promoter utilization by sigma-37 RNA polymerase. These results support a model in which sigma-37 RNA polymerase recognizes its cognate promoters by interacting with a sequence of nucleotides near the -10 region and the -35 region of the promoter--a sequence not recognized by B. subtilis sigma-55 RNA polymerase or Escherichia coli RNA polymerase.