The recE(A)⁺ gene of B subtilis and its gene product: further characterization of this universal protein

Although the SOS system of E coli and the SOB system of B subtilis share many similarities, there are distinct differences with respect to the regulation and specificity of the phenomena that constitute these global regulons. One of these differences resides in the regulation of the respective RecA and RecA-like proteins. In B subtilis the RecA-like protein, the RecE protein, shares 60% amino acid homology with its E coli counterpart. The E coli recA gene can complement most, but not all, of the functions that are lost in strains of B subtilis that do not produce a functional RecE protein. The DNA sequence of the recE⁺ gene as well as the sequence of the recE4 allele and the recA73 allele of B subtilis has demonstrated that mutants of the recE and recA loci of this bacterium actually represent alleles of the same complex gene. Accordingly, the major recombination protein of B subtilis should be referred to as RecA and the gene that encodes this protein as recA⁺.