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Cadherin‐like receptor binding facilitates proteolytic cleavage of helix α‐1 in domain I and oligomer pre‐pore formation of Bacillus thuringiensis Cry1Ab toxin
Author(s) -
Gómez Isabel,
Sánchez Jorge,
Miranda Raúl,
Bravo Alejandra,
Soberón Mario
Publication year - 2002
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(02)02321-9
Subject(s) - oligomer , manduca sexta , brush border , biochemistry , receptor , midgut , chemistry , biophysics , cleavage (geology) , trypsin , vesicle , membrane , biology , enzyme , paleontology , botany , organic chemistry , fracture (geology) , larva
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 α‐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 α‐1 and formation of a pre‐pore oligomeric structure that is efficient in pore formation, is presented.