secA341 Mutation Inhibition of Expression of the Bacillus subtilis Protease Gene, aprE

The production of extracellular protease(s) of Bacillus subtilis is induced in the post-exponential growth phase, and is severely reduced in a strain carrying a temperature sensitive mutation (secA341(ts)) in the secA gene, the product of which is required for protein secretion. The expression of the extracellular serine protease gene, aprE, as monitored by the β-galactosidase activity of an aprE-lacZ translational fusion, was inhibited in the secA341 mutant cell and restored by the introduction of the degU32(Hy) mutation, which makes the phosphorylated DegU response regulator of a two-component system refractory to dephosphorylation and causes the cell to become a strong producer of AprE. The secA341 mutation appears to block some activation step required for aprE expression.