Crystal structure of Bacillus thuringiensis Cry8Ea1: An insecticidal toxin toxic to underground pests, the larvae of Holotrichia parallela.
Crystal (Cry) proteins belong to an insect toxin family encoded and expressed by a variety of Bacillus thuringiensis isolates, and are named due to their in vivo auto-crystallization abilities. To kill the infected host insects, protease-activated Cry toxins should firstly be recognized by certain membrane receptors on the surface of insect midgut epithelial cells and consequently assemble together as lethal transmembrane pores. Here we report the 2.2-A crystal structure of Cry8Ea1 toxin, a Cry family member specifically toxic to the underground larvae of Holotrichia parallela. Superimposition of the domain I from Cry8Ea1 and other structurally characterized Cry toxins reveals an identical surface proline residue and a highly conserved kink of a helix, both of which have drawn comparatively little attention from previous researchers. Further structural analysis and functional studies suggest that both the proline and the helix kink might be essential in exposing a helix-helix hairpin, which is believed to be the very first step in the well-known "umbrella" model of the membrane penetration. In summary, we propose a plausible model of the initiation of Cry toxin domain I disassembly before membrane penetration and pore formation.
Guo
Shuyuan
S
Beijing Institute of Technology, China. guosy@bit.edu.cn
Ye
Sheng
S
Liu
Yanfeng
Y
Wei
Lei
L
Xue
Jing
J
Wu
Hongfu
H
Song
Fuping
F
Zhang
Jie
J
Wu
Xiaoai
X
Huang
Dafang
D
Rao
Zihe
Z
D000595:Amino Acid Sequence; D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry* / Q000633:toxicity*; D001517:Coleoptera / Q000187:drug effects*; D018360:Crystallography, X-Ray / Q000379:methods*; D004731:Endotoxins / Q000737:chemistry* / Q000633:toxicity*; D006460:Hemolysin Proteins / Q000737:chemistry* / Q000633:toxicity*; D007306:Insecticides / Q000737:chemistry* / Q000633:toxicity*; D007814:Larva / Q000187:drug effects; D008969:Molecular Sequence Data; D010572:Pest Control, Biological; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; C030956:insecticidal crystal protein, Bacillus Thuringiensis