Epsilon-变形菌趋化信号通路中偶联蛋白CheV与趋化受体蛋白的CZB结构域的功能研究

Functional study of coupling protein CheV and CZB domain of chemoreceptors in the Epsilon-proteobacteria chemotaxis signaling pathway

细菌通过趋化系统感知和响应外界环境变化并进行趋利避害,因此很多细菌进化出了非常复杂多样的趋化系统以适应不同的生态位。Epsilon-变形菌广泛存在于自然界中,能适应不同的生态环境,特别是深海Epsilon-变形菌能适应深海热液口和冷泉等极端环境,其趋化系统可能有其独特之处。通过BlastP和MIST数据库分析,我们发现大部分深海Epsilon-变形菌拥有F3类型趋化系统且具有单拷贝的双功能域融合蛋白CheV。此外,一种特殊结构域CZB(C-terminal Zinc-Binding)存在于深海Epsilon-变形菌的趋化受体蛋白中,而且在部分深海Epsilon-变形菌的趋化受体中还发现并鉴定了一种新的结构域CZB-like结构域。文章以Epsilon-变形菌的模式菌株空肠弯曲杆菌(Campylobacter jejuni 81-176)为研究对象,用细菌双杂交试验证实了CheV能与所有含MA结构域的趋化受体相互作用。用电感耦合等离子体质谱(ICP-Mass)技术证实了CZB-like结构域不能结合Zn离子,但细菌双杂交试验证实它能介导趋化受体Tlp9与CheV的互作。

Epsilon-proteobacteria is widely distributed,from deep-sea hydrothermal vent to surface sea water,from free-living environment to host-associated one.Chemotaxis plays an important role in bacteria survival through sensing and responding to environmental changes.Thus,some bacteria have evolved into many complex and diverse chemotaxis systems.Epsilon-proteobacteria can adapt to different environments;especially,some species can survive in the deep-sea extreme environments including hydrothermal vent and cold seep,whose chemotaxis system may have special characteristics.Bioinformatics analyses by BlastP and MIST database revealed that most Epsilon-proteobacteria species in the deep-sea hydrothermal vent have F3 type chemotaxis system.They all contain a single copy of CheV,which is a double domain fusion protein.Besides,a unique domain,CZB(C-terminal Zinc-Binding)domain,exists in chemoreceptors of deep-sea Epsilon-proteobacteria.A CZB-like domain is also identified in Epsilon-proteobacteria.Using the model strain Campylobacter jejuni 81-176,we confirmed that CheV can interact with all chemoreceptors with MA domain by bacterial two-hybrid experiments.Additionally,we demonstrated that CZB-like domain cannot bind Zn by ICP-Mass,but it can promote the interaction between chemoreceptor Tlp9 and CheV.