Crystal-forming proteins of Bacillus thuringiensis. The limited hydrolysis by endogeneous proteinases as a cause of their apparent multiplicity

Abstract

The crystals of the entomocidal protein of B. thuringiensis are admixed with proteinases that in the course of their dissolution cause gradual degradation of the genuine crystal-forming protein components (i.e., the primary biosynthetic products) to products of lower MW. This phenomenon might explain at least partially the contradictory data on the molecular parameters of the crystal-forming proteins. Preliminary inactivation of the proteinases adsorbed on the crystals allowed us to eliminate this source of the artifacts and to gain more reliable data on the protein composition of the crystals formed by various strains of B. thuringiensis. The crystals formed by all serotypes of B. thuringiensis, with the exception of the serotype V, contain only 1 protein with a MW of 145,000, 135,000 or 130,000, depending on the strain. The majority of the strains that belong to the serotype V form crystals consisting of 2 proteins with MW of 135,000 and 130,000, but some of them also have a 3rd component with a MW of 65,000.