Characterization of the insecticidal crystal protein from Bacillus thuringiensis.

Abstract

Bacillus thuringiensis produces a crystalline inclusion body composed of a 130-kDa protein which is rendered toxic upon ingestion by lepidoteran larvae. It was shown that proteinases adsorb on the surface of the crystalline body lead to proteolysis of the protein crystal especially on solubilization in alkali. Extensive washing of the protein crystal was shown to remove these proteinases and give a stable preparation. Exposure of the protein crystal to simulated sunlight results in a loss of toxicity and in the destruction of the side-chains of tryptophan, histidine, tyrosine and methionine. Destruction of amino acid side-chains is not the primary cause of the photo-inactivation of the protein crystal. The finding that all the disulfide linkages in the protein crystal are interchain and symmetrical accounts for its alkaline lability and for the high degree of conservation in the primary structure of the cystine-containing regions of the protein from various subspecies. (Abstract shortened by UMI.)