GAIN-OF-FUNCTION MUTATION OF SAPB THAT AFFECTS FORMATION OF ALKALINE-PHOSPHATASE BY BACILLUS-SUBTILIS IN SPORULATION CONDITIONS

The sapB locus was defined by mutations that render sporulation alkali ne phosphatase formation independent of sigma(F) and sigma(E) without affecting the temporal control of formation. The saps locus has been c loned and sequenced. The deduced polypeptide is 232 amino acids long, with a molecular mass of 26 kDa. It is very similar to four sequences in the database, none of which has a known function. Analysis of the t ranscription of saps indicates that it is induced during late exponent ial phase. and that maximum expression is reached during the first hou r of stationary phase, both under sporulation and non-sporulation cond itions. The defining mutations of the locus, sapB2 and sapB10, have be en sequenced and found to contain the same change, a G --> A transitio n resulting in an Ala(111)Thr switch. This mutation apparently results in a gain-of-function, as saps null mutants are indistinguishable fro m sap(+) strains in terms of their APase production during sporulation .