The pre-pore from Bacillus thuringiensis Cry1Ab toxin is necessary to induce insect death in Manduca sexta.
The insecticidal Cry toxins from Bacillus thuringiensis bacteria are pore-forming toxins that lyse midgut epithelial cells in insects. We have previously proposed that they form pre-pore oligomeric intermediates before membrane insertion. For formation of these oligomers coiled-coil structures are important, and helix alpha-3 from Cry toxins could form coiled-coils. Our data shows that different mutations in helix alpha-3 are affected in pore formation and toxicity. Mutants affected in toxicity bind Bt-R(1) receptor with a similar K(D) as the wild type toxin but do not form oligomers nor induce pore formation in planar lipid bilayers, indicating that the pre-pore oligomer is an obligate intermediate in the intoxication of Cry1Ab toxin and that interaction of monomeric Cry1Ab with Bt-R(1) is not enough to kill susceptible larvae.
Jiménez-Juárez
N
N
Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico.
Muñoz-Garay
C
C
Gómez
I
I
Gill
S S
SS
Soberón
M
M
Bravo
A
A
D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001427:Bacterial Toxins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004064:Digestive System / Q000378:metabolism; D004731:Endotoxins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006460:Hemolysin Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018402:Manduca / Q000378:metabolism*; D009154:Mutation; D011485:Protein Binding
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis