Two conformational states of the membrane-associated Bacillus thuringiensis Cry4Ba delta-endotoxin complex revealed by electron crystallography: implications for toxin-pore formation.
Two conformational states of the membrane-associated Bacillus thuringiensis Cry4Ba delta-endotoxin complex revealed by electron crystallography: implications for toxin-pore formation.
复制标题
电子晶体学揭示的膜相关苏云金芽孢杆菌 Cry4Ba δ-内毒素复合物的两种构象状态：对毒素孔形成的影响。
DOI：
10.1016/j.bbrc.2007.07.086
复制
发表时间：
2007
影响因子：
3.1
通讯作者：
Angsuthanasombat,Chanan
中科院分区：
文献类型：
--
作者：
Ounjai,Puey;Unger,VinzenzM;Sigworth,FredJ;Angsuthanasombat,Chanan
由苏云金芽孢杆菌产生的Cry δ-内毒素的杀虫性质通常被认为是由它们在易感昆虫幼虫的中肠细胞膜中形成裂解孔的能力引起的。在这里，我们分析了膜相关结构的65 kDa的双翅目活性Cry 4 Ba毒素的电子晶体学。在DMPC存在下，通过洗涤剂透析使膜相关毒素复合物结晶。根据吸附表面的电荷，寡聚毒素复合物的2D晶体已被捕获在两个不同的构象。这些晶体的投影图已在17 μ m分辨率下生成。这两种复合物似乎是三聚体;在一种晶体形式中，其投影结构显示出对称的风车状形状，在复合物的中间几乎没有凹陷。另一种形式显示出螺旋桨状的构造，在中心区域显示出明显的孔，推测代表毒素诱导的孔。因此，这些晶体学数据首次表明，65 kDa的激活Cry 4 Ba毒素与脂质膜可以存在于至少两种不同的三聚体构象，可以想象的是，这意味着封闭和开放状态的孔。
The insecticidal nature of Cry δ-endotoxins produced by Bacillus thuringiensis is generally believed to be caused by their ability to form lytic pores in the midgut cell membrane of susceptible insect larvae. Here we have analyzed membrane-associated structures of the 65-kDa dipteran-active Cry4Ba toxin by electron crystallography. The membrane-associated toxin complex was crystallized in the presence of DMPC via detergent dialysis. Depending upon the charge of the adsorbed surface, 2D crystals of the oligomeric toxin complex have been captured in two distinct conformations. The projection maps of those crystals have been generated at 17Å resolution. Both complexes appeared to be trimeric; as in one crystal form, its projection structure revealed a symmetrical pinwheel-like shape with virtually no depression in the middle of the complex. The other form revealed a propeller-like conformation displaying an obvious hole in the center region, presumably representing the toxin-induced pore. These crystallographic data thus demonstrate for the first time that the 65-kDa activated Cry4Ba toxin in association with lipid membranes could exist in at least two different trimeric conformations, conceivably implying the closed and open states of the pore.