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.

枯草芽孢杆菌（Bacillus subtilis）α-淀粉酶基因（alpha-amylase gene，amyE）的分解代谢物阻遏（catabolite repression），涉及位于启动子（promoter）下游且与转录起始位点（transcription start site）重叠的操纵序列（operator sequence，amyR）。通过对该序列实施寡核苷酸定点诱变（oligonucleotide site-directed mutagenesis），可鉴定出参与分解代谢物阻遏的必需碱基位点。两类突变不仅增强了该操纵序列的2倍对称性，同时提升了阻遏比率（repression ratio）。尽管多数突变使阻遏比率下降3至11倍，但部分突变还可使淀粉酶产量（amylase production）提升2倍及以上。另有部分突变仅引发淀粉酶过量合成，却不影响分解代谢物阻遏过程。其他受分解代谢物阻遏的枯草芽孢杆菌启动子中存在的同源序列（homologous sequences），提示一类共同的调控位点（regulatory site）可能参与了分解代谢物阻遏调控。