Cytotoxicity of the Bacillus cereus Nhe Enterotoxin Requires Specific Binding Order of Its Three Exoprotein Components
Cytotoxicity of the Bacillus cereus Nhe Enterotoxin Requires Specific Binding Order of Its Three Exoprotein Components
复制标题
DOI：
10.1128/iai.00247-10
复制
发表时间：
2010-09-01
影响因子：
3.1
通讯作者：
Maertlbauer, Erwin
中科院分区：
文献类型：
--
作者：
Lindback, Toril;Hardy, Simon P.;Maertlbauer, Erwin
本研究的重点是蜡状芽孢杆菌Nhe肠毒素的三个组件的相互作用，特别强调NheB和NheC的功能作用。结果表明，NheB和NheC都能够直接与Vero细胞结合，而NheA缺乏这种能力。还显示Nhe诱导的细胞毒性需要各个组分的特定结合顺序，由此在引发步骤中NheC的存在以及在最终孵育步骤中NheA的存在是强制性的。在第二步中单独用NheB引发细胞和添加NheA加NheC未能诱导毒性作用。此外，在溶液中，过量的NheC抑制NheB与Vero细胞的结合，而如果在添加NheB之前去除未结合的NheC，则用过量的NheC引发细胞导致完全毒性。通过使用突变的NheC蛋白，其中预测的β-舌中的两个半胱氨酸残基被甘氨酸（NheC（cys-））替换或其中整个疏水段被删除（NheC（hr-）），发现NheC的预测的疏水β-舌对于结合细胞膜是必需的，但对于与溶液中的NheB的相互作用不是必需的。这里提供的所有数据都与以下模型兼容。Nhe作用模式的第一步与NheC和NheB与细胞表面的结合有关，并且可能伴随着构象变化。这些事件允许随后结合NheA，导致细胞裂解。
This study focuses on the interaction of the three components of the Bacillus cereus Nhe enterotoxin with particular emphasis on the functional roles of NheB and NheC. The results demonstrated that both NheB and NheC were able to bind to Vero cells directly while NheA lacked this ability. It was also shown that Nhe-induced cytotoxicity required a specific binding order of the individual components whereby the presence of NheC in the priming step as well as the presence of NheA in the final incubation step was mandatory. Priming of cells with NheB alone and addition of NheA plus NheC in the second step failed to induce toxic effects. Furthermore, in solution, excess NheC inhibited binding of NheB to Vero cells, whereas priming of cells with excess NheC resulted in full toxicity if unbound NheC was removed before addition of NheB. By using mutated NheC proteins where the two cysteine residues in the predicted beta-tongue were replaced with glycine (NheC(cys-)) or where the entire hydrophobic stretch was deleted (NheC(hr-)), the predicted hydrophobic beta-tongue of NheC was found essential for binding to cell membranes but not for interaction with NheB in solution. All data presented here are compatible with the following model. The first step in the mode of action of Nhe is associated with binding of NheC and NheB to the cell surface and probably accompanied by conformational changes. These events allow subsequent binding of NheA, leading to cell lysis.