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 nonhyd rolyzable analogs stimulate the formation of the SpoIIAB.sigma(F) comp lex, whereas ADP stimulates the formation of the SpoIIAB.SpoIIAA compl ex. Which protein SpoIIAB associates with is determined by the concent rations of the two nucleotides, on which basis we propose a partner-sw itching model for the regulation of sigma(F): GRAPHICS Consistent wi th this model, SpollAA reverses SpoIIAB-mediated inhibition of sigma(F )-directed transcription in a manner that depends on ADP. Cell-specifi c activation of of could be due to an alteration in adenosine nucleoti de levels in one cell of the sporangium.