Transcriptional regulation of the Bacillus subtilis bscR-CYP102A3 operon by the BscR repressor and differential induction of cytochrome CYP102A3 expression by oleic acid and palmitate

The adjacent yrhI and yrhJ genes were identified by the Bacillus subtilis g enome sequencing project. We now report that yrhJ (renamed CYP102A3) encode s a cytochrome P450 and that yrhI (renamed bscR) encodes a repressor that n egatively regulates the transcription of the bscR-CYP102A3 operon. The tran scriptional initiation site of bscR has been mapped by primer extension ana lysis. An 18-bp perfect palindromic sequence centered 65.5 bp downstream fr om the transcriptional initiation site of bscR has been identified as the b inding site for BscR by gel mobility shift assays. Base substitutions in th e 18-bp inverted repeat resulted in derepression of the bscR-xylE transcrip tional fusion in vivo. bscR-xylE fusion studies and Northern blot analysis revealed that oleic acid and palmitate could induce the expression of the b scR-CYP102A3 operon to a considerable extent. However, only oleic acid was capable of preventing the binding of BscR to its operator DNA in vitro, sug gesting that the induction of CYP102A3 expression by oleic acid and palmita te in B. subtilis might be mediated through different mechanisms.