title: Identification of Bacillus thuringiensis Cry3Aa toxin domain II loop 1 as the binding site of Tenebrio molitor cadherin repeat CR12.
abstract: Bacillus thuringiensis Cry toxins exert their toxic effect by specific recognition of larval midgut proteins leading to oligomerization of the toxin, membrane insertion and pore formation. The exposed domain II loop regions of Cry toxins have been shown to be involved in receptor binding. Insect cadherins have shown to be functionally involved in toxin binding facilitating toxin oligomerization. Here, we isolated a VHH (VHHA5) antibody by phage display that binds Cry3Aa loop 1 and competed with the binding of Cry3Aa to Tenebrio molitor brush border membranes. VHHA5 also competed with the binding of Cry3Aa to a cadherin fragment (CR12) that was previously shown to be involved in binding and toxicity of Cry3Aa, indicating that Cry3Aa binds CR12 through domain II loop 1. Moreover, we show that a loop 1 mutant, previously characterized to have increased toxicity to T. molitor, displayed a correlative enhanced binding affinity to T. molitor CR12 and to VHHA5. These results show that Cry3Aa domain II loop 1 is a binding site of CR12 T. molitor cadherin.
authors.affiliation: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico.
authors.forename: Fernando
authors.initials: F
authors.lastname: Zúñiga-Navarrete
authors.affiliation: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico.
authors.forename: Isabel
authors.initials: I
authors.lastname: Gómez
authors.affiliation: Centro de Investigaciones Biológicas, Universidad Autónoma del Estado de Morelos, Avenida Universidad 1001, Colonia Chamilpa, Cuernavaca 62209, Morelos, Mexico.
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Peña
authors.affiliation: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico.
authors.forename: Itzel
authors.initials: I
authors.lastname: Amaro
authors.affiliation: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Ortíz
authors.affiliation: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico.
authors.forename: Baltazar
authors.initials: B
authors.lastname: Becerril
authors.affiliation: CINVESTAV IPN Unidad Irapuato, Apdo. Postal 629, 36500 Irapuato, Gto, Mexico.
authors.forename: Jorge E
authors.initials: JE
authors.lastname: Ibarra
authors.affiliation: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Bravo
authors.affiliation: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico. Electronic address: mario@ibt.unam.mx.
authors.forename: Mario
authors.initials: M
authors.lastname: Soberón
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001413:Bacillus thuringiensis / Q000378:metabolism*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D015820:Cadherins / Q000378:metabolism*; D004731:Endotoxins / Q000378:metabolism*; D006460:Hemolysin Proteins / Q000378:metabolism*; D019476:Insect Proteins / Q000378:metabolism*; D007814:Larva / Q000378:metabolism; D008871:Microvilli / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D020449:Repetitive Sequences, Amino Acid; D013712:Tenebrio / Q000378:metabolism*
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D015820:Cadherins; D004731:Endotoxins; D006460:Hemolysin Proteins; D019476:Insect Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis
keywords: Bacillus thuringiensis; Cry3Aa toxin; Phage display; Receptor binding; Tenebrio molitor; VHH antibodies