Identification of two proteins encoded by com, a competence control locus of Streptococcus pneumoniae

The com locus, which controls competence for genetic transformation in Streptococcus pneumoniae, was analyzed by construction of a series of subclones, insertion mutations, and deletions of the cloned DNA in Escherichia coli. In vitro transcription-translation of these com plasmids revealed two neighboring genes, comA and comB, encoding proteins of 77,000 and 49,000 daltons, respectively. Their map positions and orientations were determined. Insertions in either gene eliminated the corresponding protein and had no effect on the other. In addition, a 15,000-dalton com protein was tentatively identified, although the exact location of this gene remains to be determined. Features of the DNA adjacent to the com locus are also described.