The intracellular Ca(2+)-dependent serine proteinase (ISP1) activity in the cytoplasm of nongrowing Bacillus megaterium incubated in a sporulation medium was determined at 35 degrees C and at temperatures decreasing the sporulation frequency (42 degrees C) or suppressing sporulation (43.5 degrees C). The enzyme in the crude cytoplasmic fraction was partially inhibited by a loosely bound inhibitor(s) because the ISP1 activity rose after protein fractionation by HPLC. Temperature shift-up or osmotic stress applied at 35 degrees C increased the development of the ISP1 activity several times. The increase was caused at least partially by the synthesis of the enzyme protein, as proved by SDS-PAGE and immunoblotting of the cytoplasm. This enzyme thus probably belongs among heat-shock proteins.

Department of Molecular and Cellular Microbiology Academy of Sciences of the Czech Republic Prague

General and molecular microbiology and microbial genetics in the IM CAS

Oxidative stress in microorganisms--I. Microbial vs. higher cells--damage and defenses in relation to cell aging and death

Intracellular serine proteinase behaves as a heat-stress protein in nongrowing but as a cold-stress protein in growing populations of Bacillus megaterium