The genes lepA and hemN form a bicistronic operon in Bacillus subtilis

The lepA operon of Bacillus subtilis was found to be bicistronic and to consist of the two genes lepA and hemN, which encode a putative GTP-binding protein and an oxygen-independent coproporhyrinogen III oxidase, respectively. The lepA operon is located immediately upstream of the dnaK operon. Both operons are transcribed in the same direction and are not separated by an obvious transcription-terminator-like structure. The lepA operon is preceded by a potential vegetative promoter, and there is a putative strong intergenic terminator between lepA and hemN. Northern blot experiments revealed only a transcript corresponding to legA, but expression of hemN was demonstrated in slot-blot and immunoblot experiments using antibodies raised against His-tagged HemN. The data suggest that most of the transcripts originating at the potential vegetative promoter are terminated at the intergenic terminator, Readthrough transcription into the downstream dnaK operon was not found.