The subtilisin E gene of Bacillus subtilis is transcribed from a sigma 37 promoter in vivo

A cloned Bacillus subtilis gene (sprE) expressed only during the stationary growth phase is shown to encode the subtilisin E protease, an enzyme associated with sporulation. We have determined the DNA sequence of the sprE promoter region and the promoter-proximal half of the structural gene. The sprE gene codes for a putative 29-residue signal peptide and a 77-residue leader peptide preceding the mature subtilisin sequence. By plasmid integration and phage PBS1 transduction, we have mapped the sprE locus between glyB and metD on the B. subtilis chromosome, a region also containing the hyperprotease-producing hpr gene. In vitro the sprE gene is transcribed by the minor form of RNA polymerase containing a 37,000-dalton sigma factor (sigma 37). We show by S1 nuclease mapping that sprE transcription initiates at dual start sites both in vitro and in vivo and that the promoter for the downstream site has a characteristic sigma 37 recognition sequence. We propose that the physiological role of the sigma 37 RNA polymerase is to transcribe a class of genes that are catabolite repressed, that encode extracellular enzymes, or that are expressed only during the stationary phase of growth.