title: N-terminal activation is an essential early step in the mechanism of action of the Bacillus thuringiensis Cry1Ac insecticidal toxin.
abstract: A variant form of the Bacillus thuringiensis Cry1Ac toxin that is not cleaved at the N terminus during proteolytic activation with trypsin was found to be incapable of forming pores in Manduca sexta brush border membrane vesicles in vitro and had reduced insecticidal activity in vivo. Binding studies indicated an altered binding pattern of the mutant toxin in that bound toxin could not be fully displaced by a high molar excess of fully trypsin-activated toxin. These results suggest that proteolytic removal of the N-terminal peptide of Cry1Ac is an important step in toxin activation.
authors.affiliation: Insituto de Biotechnologia, Universidad Nacional Autónoma de México, Morelos 62210, México.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Bravo
authors.forename: Jorge
authors.initials: J
authors.lastname: Sanchez
authors.forename: Thaleia
authors.initials: T
authors.lastname: Kouskoura
authors.forename: Neil
authors.initials: N
authors.lastname: Crickmore
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000378:metabolism*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics / Q000633:toxicity*; D001427:Bacterial Toxins / Q000235:genetics / Q000633:toxicity*; D001665:Binding Sites; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D004731:Endotoxins / Q000235:genetics / Q000633:toxicity*; D006460:Hemolysin Proteins; D018402:Manduca / Q000187:drug effects*; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D010572:Pest Control, Biological; D011188:Potassium / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D014357:Trypsin; D011188:Potassium