An adenosine nucleotide switch controlling the activity of a cell type-specific transcription factor in B. subtilis.

The sigma F factor establishes cell type-specific gene transcription during sporulation in B. subtilis. sigma F is negatively regulated by SpollAB, which forms complexes with sigma F or SpollAA. ATP and its nonhydrolyzable analogs stimulate the formation of the SpollAB.sigma F complex, whereas ADP stimulates the formation of the SpollAB.SpollAA complex. Which protein SpollAB 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: [formula: see text] Consistent with this model, SpollAA reverses SpollAB-mediated inhibition of sigma F-directed transcription in a manner that depends on ADP. Cell-specific activation of sigma F could be due to an alteration in adenosine nucleotide levels in one cell of the sporangium.