CHARACTERIZATION OF COME, A LATE COMPETENCE OPERON OF BACILLUS-SUBTILIS REQUIRED FOR THE BINDING AND UPTAKE OF TRANSFORMING DNA

The binding and transport of DNA by competent Bacillus subtilis requir es the assembly of a specialized apparatus. We present here the charac terization of comE, an operon under competence control that is require d for both DNA binding to the competent cell surface, and for uptake. comE contains three open reading frames (ORF1-3) read in the forward d irection, preceded by a long untranslated leader sequence and an appar ent Esigma(A) promoter. A minor promoter also is responsible for trans cription of ORF2 and -3. A transcript containing a single ORF is produ ced in the reverse direction. The reverse ORF overlaps ORF1 and the un translated comE leader. The comE transcript is present at a very low l evel during growth and at an elevated level in stationary-phase cells. Conversely, the reverse transcript is present during exponential grow th and disappears during stationary phase. The reverse ORF resembles p rokaryotic and eukaryotic pyrroline-5'-carboxylate reductases, while O RF2 is similar to several dCMP deaminases. ORF1 and ORF3 are predicted to be integral membrane proteins. The latter is specifically required for DNA uptake but not for binding.