Identification and purification of the 69-kDa intracellular protease involved in the proteolytic processing of the crystal δ-endotoxin of Bacillus thuringiensis subsp. tenebrionis

Abstract The dynamics of appearance of intracellular proteases in relation to the synthesis of crystal δ-endotoxin was studied to identify the native intracellular protease(s) involved in the proteolytic processing of the 73-kDa protoxin of Bacillus thuringiensis subsp. tenebrionis. In vitro proteolytic activation of the 73-kDa protoxin indicated the possible role of 69-kDa protease in the proteolytic processing of 73-kDa protoxin. The purified 69-kDa protease was able to cause the proteolytic activation of the 73-kDa protoxin to 68-kDa toxin and this conversion was inhibited by ethylenediamine tetraacetic acid and 1,10-phenanthroline.