title: Characterization of the entomocidal parasporal crystal of Bacillus thuringiensis.
abstract: The parasporal crystalline protoxin of Bacillus thuringiensis contains a single glycoprotein subunit that has a molecular weight of approximately 1.2 X 10(5). The carbohydrate consists of glucose (3.8%) and mannose (1.8%). At alkaline pH, the proendotoxin is apparently solubilized and activated by an autolytic mechanism involving an inherent sulfhydryl protease that renders the protoxin insecticidal. Activation generates protons, degraded polypeptides, sulfhydryl group reactivity, proteolytic activity, and insect toxicity. Chemical modification of the sulfhydryl groups inhibits the proteolytic and insecticidal activities, suggesting that cysteine residues may be present in the active site of the protein.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D001413:Bacillus thuringiensis / Q000032:analysis*; D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000032:analysis* / Q000633:toxicity; D001681:Biological Assay; D003460:Crystallization; D004591:Electrophoresis, Polyacrylamide Gel; D005947:Glucose / Q000032:analysis; D008358:Mannose / Q000032:analysis; D008970:Molecular Weight; D009036:Moths / Q000187:drug effects; D012995:Solubility; D013171:Spores, Bacterial
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D005947:Glucose; D008358:Mannose