Oligomerization of Clostridium perfringens ε-toxin is dependent upon membrane fluidity in liposomes
Oligomerization of Clostridium perfringens ε-toxin is dependent upon membrane fluidity in liposomes
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DOI：
10.1021/bi051805s
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发表时间：
2006-01-10
期刊：
影响因子：
2.9
通讯作者：
Sakurai, J
中科院分区：
文献类型：
--
作者：
Nagahama, M;Hara, H;Sakurai, J
产气荚膜梭菌ε毒素与MDCK细胞上的受体结合并在膜中形成七聚体。用不同磷脂酰胆碱（PC）组成的羧基荧光素（CF）脂质体研究了ε-毒素寡聚化的机制。毒素导致CF以剂量依赖性方式从脂质体中泄漏。毒素诱导的CF泄漏，毒素与脂质体的结合，以及功能性寡聚体的形成随着脂质体中使用的PC的相变温度（T-m）降低而增加。使用HPA传感器芯片（BIAcore）的表面等离子体共振分析还揭示毒素与脂质体的结合随着脂质体中使用的PC的Tm的降低而增加。标记了在3-（三氟甲基）-3-（间-[I-125]碘苯基）二氮杂环丙烯（[I-125]TID）处理的脂质体中形成的寡聚体，表明其插入疏水区域。此外，ε-毒素诱导的CF渗漏率通过用磷脂酰乙醇胺或二酰基甘油处理而增强，已知其有利于层状到倒置六方（L-H）相变。我们发现，脂质体中的膜流动性在毒素与脂质体的结合、插入脂质体双层中的疏水区域以及在双层中的组装过程中起着重要作用。
Clostridium perfringens epsilon-toxin binds to receptors on MDCK cells and forms a heptamer in membranes. The mechanism behind the oligomerization of epsilon-toxin was studied using carboxyfluorescein (CF)-loaded liposomes composed of various phosphatidylcholines (PCs). The toxin caused CF to leak from liposomes in a dose-dependent manner. The toxin-induced leakage of CF, binding of the toxin to liposomes, and formation of a functional oligomer increased as the phase-transition temperature (T-m) of the PC used in the liposomes decreased. Surface plasmon resonance analysis using an HPA sensorchip (BIAcore) also revealed that the binding of the toxin to liposomes increased with a decrease in the Tm of the PC used in liposomes. The oligomer that was formed in 3-(trifluoromethyl)-3-(m-[I-125]iodophenyl)diazirine ([I-125]TID)-treated liposomes was labeled, indicating that it inserts into a hydrophobic region. Furthermore, the rate of epsilon-toxin-induced CF leakage was enhanced by treatment with phosphatidylethanolamine or diacylglycerol, which is known to favor a lamellar-to-inverted hexagonal (L-H) phase transition. We show that membrane fluidity in the liposome plays an important role in the binding of the toxin to liposomes, insertion into the hydrophobic region in the bilayer of liposomes, and the assembly process in the bilayer.