title: Cadherin-like receptor binding facilitates proteolytic cleavage of helix alpha-1 in domain I and oligomer pre-pore formation of Bacillus thuringiensis Cry1Ab toxin.
abstract: Cry toxins form lytic pores in the insect midgut cells. The role of receptor interaction in the process of protoxin activation was analyzed. Incubation of Cry1Ab protoxin with a single chain antibody that mimics the cadherin-like receptor and treatment with Manduca sexta midgut juice or trypsin, resulted in toxin preparations with high pore-forming activity in vitro. This activity correlates with the formation of a 250 kDa oligomer that lacks the helix alpha-1 of domain I. The oligomer, in contrast with the 60 kDa monomer, was capable of membrane insertion as judged by 8-anilino-1-naphthalenesulfonate binding. Cry1Ab protoxin was also activated to a 250 kDa oligomer by incubation with brush border membrane vesicles, presumably by the action of a membrane-associated protease. Finally, a model where receptor binding allows the efficient cleavage of alpha-1 and formation of a pre-pore oligomeric structure that is efficient in pore formation, is presented.
authors.affiliation: Instituto de Biotecnología, Departamento de Microbiología Molecular, UNAM, Apdo postal 510-3, Cuernavaca, 62250, Morelos, Mexico.
authors.forename: Isabel
authors.initials: I
authors.lastname: Gómez
authors.forename: Jorge
authors.initials: J
authors.lastname: Sánchez
authors.forename: Raúl
authors.initials: R
authors.lastname: Miranda
authors.forename: Alejandra
authors.initials: A
authors.lastname: Bravo
authors.forename: Mario
authors.initials: M
authors.lastname: Soberón
mesh_terms: D001413:Bacillus thuringiensis / Q000378:metabolism*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001427:Bacterial Toxins; D015820:Cadherins / Q000378:metabolism*; D010450:Endopeptidases / Q000378:metabolism; D004731:Endotoxins / Q000737:chemistry / Q000378:metabolism*; D006460:Hemolysin Proteins; D010447:Peptide Hydrolases / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D015820:Cadherins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D010450:Endopeptidases; D010447:Peptide Hydrolases