Site-directed mutagenesis of a catabolite repression operator sequence in Bacillus subtilis

Catabolite repression of the Bacillus subtilis alpha-amylase gene (amyE) involves an operator sequence located just downstream of the promoter (amyR), overlapping the transcription start site. Oligonucleotide site-directed mutagenesis of this sequence identified bases required for catabolite repression. Two mutations increased both the 2-fold symmetry of the operator and the repression ratio. Although many mutations reduced the repression ratio 3- to 11-fold, some also caused a 2-fold or greater increase in amylase production. Others caused hyperproduction without affecting catabolite repression. Homologous sequences in other catabolite-repressed B. subtilis promoters suggest a common regulatory site may be involved in catabolite repression.