AN ADENOSINE NUCLEOTIDE SWITCH CONTROLLING THE ACTIVITY OF A CELL-TYPE-SPECIFIC TRANSCRIPTION FACTOR IN BACILLUS-SUBTILIS

The sigma(F) factor establishes cell type-specific gene transcription during sporulation in B. subtilis. sigma(F) is negatively regulated by SpoIIAB, which forms complexes with of or SpoIIAA. ATP and its nonhydrolyzable analogs stimulate the formation of the SpoIIAB.sigma(F) complex, whereas ADP stimulates the formation of the SpoIIAB.SpoIIAA complex. Which protein SpoIIAB associates with is determined by the concentrations of the two nucleotides, on which basis we propose a partner-switching model for the regulation of sigma(F): [GRAPHICS] Consistent with this model, SpollAA reverses SpoIIAB-mediated inhibition of sigma(F)-directed transcription in a manner that depends on ADP. Cell-specific activation of of could be due to an alteration in adenosine nucleotide levels in one cell of the sporangium.