Lipid-induced pore formation of the Bacillus thuringiensis Cry1Aa insecticidal toxin.
After activation, Bacillus thuringiensis (Bt) insecticidal toxin forms pores in larval midgut epithelial cell membranes, leading to host death. Although the crystal structure of the soluble form of Cry1Aa has been determined, the conformation of the pores and the mechanism of toxin interaction with and insertion into membranes are still not clear. Here we show that Cry1Aa spontaneously inserts into lipid mono- and bilayer membranes of appropriate compositions. Fourier Transform InfraRed spectroscopy (FTIR) indicates that insertion is accompanied by conformational changes characterized mainly by an unfolding of the beta-sheet domains. Moreover, Atomic Force Microscopy (AFM) imaging strongly suggests that the pores are composed of four subunits surrounding a 1.5 nm diameter central depression.
Vié
V
V
CRBM, CNRS-UPR 1086, 1919 route de Mende, 34293 Montpellier, France.
Van Mau
N
N
Pomarède
P
P
Dance
C
C
Schwartz
J L
JL
Laprade
R
R
Frutos
R
R
Rang
C
C
Masson
L
L
Heitz
F
F
Le Grimellec
C
C
D001413:Bacillus thuringiensis; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000378:metabolism*; D001427:Bacterial Toxins / Q000378:metabolism*; D004731:Endotoxins / Q000378:metabolism*; D006460:Hemolysin Proteins; D007306:Insecticides / Q000378:metabolism*; D008051:Lipid Bilayers / Q000378:metabolism*; D050356:Lipid Metabolism; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D014867:Water / Q000378:metabolism
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; D008051:Lipid Bilayers; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D014867:Water