COMF, A BACILLUS-SUBTILIS LATE COMPETENCE LOCUS, ENCODES A PROTEIN SIMILAR TO ATP-DEPENDENT RNA DNA HELICASES

We have sequenced and genetically characterized comF, a Bacillus subti lis competence locus, previously identified by Tn917 transposon insert ion mutagenesis. Expression of the locus, in which three open reading frames (ORFs) were found, is driven by a single sigma(A)-like promoter in front of comFORF1 and is dependent on early regulatory competence genes and only expressed in competence medium. The predicted amino aci d sequences of two of the ORFs showed similarities to known proteins i n the Gen-Bank and SwissProt databases: ComFORF1 is similar to an exte nsive family of ATP-dependent RNA/DNA helicases with closer similarity to the DEAD protein subfamily and to the PriA protein in Escherichia coli. The latter is a DNA translocase/helicase required for primosome assembly at the replication fork of phage phiX174. ComFORF3 is 22% ide ntical to Com101, a protein required for genetic competence in Haemoph ilus influenzae, a naturally competent Gram-negative bacterium. In-fra me comFORF1 deletions were 1000-fold deficient in transformability com pared to the wild type, whereas disruptions of the other two ORFs were only five- to 10-fold lower. These observations allow us to hypothesi ze that the ComFORF1 late gene product plays an essential role during the binding and uptake events involved in Bacillus subtilis transforma tion.