The 130 kDa polypeptide appears to be the most susceptible of the polypeptides constituting the Bacillus thuringiensis ssp. israelensis δ-endotoxin to the proteases associated with sporulation. Stabilization of this polypeptide in the recently described K-S sporulation medium has been achieved through limiting its cleavage by removing contaminating proteases from the culture by washing. In this way, the complete δ-endotoxin profile is retained for studies on all of the constituent polypeptide fractions.
