期刊
JOURNAL OF STRUCTURAL BIOLOGY
卷 168, 期 2, 页码 259-266出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jsb.2009.07.004
关键词
Bacillus thuringiensis; Bioinsecticide; Cry protein; Crystal structure
资金
- Major State Basic Research Development Program of China (973 Program) [2009CB118902]
- National High Technology Research and Development Program of China (863 Program) [2006AA02Z189, 2006AA10A212]
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-angstrom 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. (C) 2009 Elsevier Inc. All rights reserved.
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