Construction and properties of an intracellular serine protease mutant of Bacillus subtilis

An intracellular serine protease (ISP-1) mutant of Bacillus subtilis was created by introducing a frameshift into the coding region of the cloned gene. Intracellular protease activity in the mutant was very low, yet sporulation in both nutrient broth and minimal medium was normal. The rate of bulk protein turnover in the mutant was slightly slower than that in the wild-type strain. These results suggest that the gene for ISP-1 is not essential and that ISP-1 is not the major enzyme involved in protein turnover during sporulation.