CATABOLITE REPRESSION OF THE BACILLUS-SUBTILIS-HUT OPERON REQUIRES A CIS-ACTING SITE LOCATED DOWNSTREAM OF THE TRANSCRIPTION INITIATION SITE

Expression of the Bacillus subtilis hut operon is subject to regulatio n by catabolite repression. A set of hut-lacZ transcriptional fusions was constructed and used to identify two cis-acting sites involved in catabolite repression. The hutO(CR1) operator site lies immediately do wnstream of the hut promoter and weakly regulates hut expression in re sponse to catabolite repression. The downstream hutO(CR2) operator sit e lies within the hutP gene, between positions +203 and +216, and is r equired for wild-type levels of catabolite repression. Both the hutO(C R1) and hutO(CR2) operators have sequence similarity to the sites whic h mediate catabolite repression of several other B. subtilis genes. Tw o mutations which relieve catabolite repression of hut expression were found to alter the nucleotide sequence of the hutO(CR2) operator. Cat abolite repression of hut expression was partially relieved in strains containing the ccpA mutation but not in strains containing either the pai or hpr mutation.