EXTRACELLULAR SIGNAL PROTEIN TRIGGERING THE PROTEOLYTIC ACTIVATION OFA DEVELOPMENTAL TRANSCRIPTION FACTOR IN BACILLUS-SUBTILIS

We present biochemical evidence for an intercellular signal transducti on pathway in B. subtilis. This pathway governs the conversion of the proprotein pro-sigma(E) to the mature transcription factor rho(E). Pro teolytic processing is mediated by the membrane protein SpoIIGA and is triggered by the inferred extracellular signal protein SpoIIR. A fact or in conditioned medium from B. subtilis cells engineered to produce SpoIIR during growth triggered processing in protoplasts of B. subtili s cells that had been engineered to produce SpoIIGA and pro-sigma(E). The factor was also detected in, and partially purified from, extracts of SpoIIR-producing cells of E. coli. We speculate that SpoIIGA is bo th a receptor and a protease and that SpoIIR interacts with SpoIIGA on the outside of the cytoplasmic membrane, activating the intracellular protease domain of SpoIIGA.