DIMER FORM OF PHOSPHORYLATED SPO0A, A TRANSCRIPTIONAL REGULATOR, STIMULATES THE SPO0F TRANSCRIPTION AT THE INITIATION OF SPORULATION IN BACILLUS-SUBTILIS

The SpoOA protein of Bacillus subtilis is a transcriptional regulator that shows extensive homology to the regulator proteins in bacterial two-component regulatory systems. Phosphorylation of SpoOA is absolutely necessary for the initiation of sporulation. We now show that phospho-SpoOA is a dimer, binds specifically to the spoOF promoter region, and stimulates the transcription from the P2 promoter recognized by sigma(H)-RNA polymerase. Biochemical and biological analyses suggest that phospho-SpoOA interacts directly with the ''OA-like box'' sequence (TGTCGTA) located in the spoOF promoter region. Phosphorylation of SpoOA enhanced its affinity to the OA-like box. Evidence is also presented that the spoOF promoter region contains a static bend having two sets of oligo(dA-dT) tracts. It was demonstrated that the bending region overlaps with the recognition site for the phospho-SpoOA.