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结核分枝杆菌作为肺结核病的病原菌,在人类中致死率远高于其他病原菌.结核分枝杆菌具有特殊的疏水性细胞壁结构,这种致密的细胞壁结构帮助结核分枝杆菌抵御外界环境压力和来自宿主细胞的毒素.同时,它利用特殊的分泌系统将体内的毒力蛋白输出体外,ESX-1分泌系统就是其中之一.结核分枝杆菌ESX-1系统在结核分枝杆菌进入宿主细胞吞噬小体、逃逸至细胞质以及杀死吞噬细胞这些过程中发挥重要作用.研究表明,在结核分枝杆菌内膜上存在一个由多亚基组成、旨在帮助结核分枝杆菌向外输送分泌蛋白的分泌装置.在这个分泌装置的帮助下,结核分枝杆菌重要的毒力蛋白ESAT-6跨内膜向外分泌,EspB也通过这个内膜上的分泌装置被转运至胞外.EspB存在于静置培养的结核分枝杆菌的胶囊层中,也可在振荡培养的结核分枝杆菌的培养液中被检测.通过X射线晶体衍射分析,我们解析了EspB的晶体结构,相比于其他同源结构,发现了EspB的不同构象,即EspB单体能够自组装成为七聚体的规则结构,联系其与毒力因子ESAT-6具有共分泌的特点,七聚体构象的发现为解释EspB在结核分枝杆菌向外分泌蛋白的过程中发挥的作用提供线索,即EspB具有锚定在结核分枝杆菌胶囊层中,作为运输ESAT-6的孔道而存在的可能.
Mycobacterium tuberculosis, as the pathogen of pulmonary tuberculosis, has a much higher lethality in humans than other pathogens.Mycobacterium tuberculosis has a special hydrophobic cell wall structure, which helps Mycobacterium tuberculosis to withstand the pressure from the external environment and comes from Host cell toxins at the same time, it uses a special secretion system to export the body of virulence proteins in vitro, the ESX-1 secretion system is one of the Mycobacterium tuberculosis ESX-1 system in the host cell into the small swallowed Mycobacterium tuberculosis Body, escaping to the cytoplasm and killing phagocytes.Studies have shown that there is a multi-subunit on the inner membrane of Mycobacterium tuberculosis that is designed to help Mycobacterium tuberculosis deliver secretion of secreted proteins With the help of this secretion device, the important virulence protein ESAT-6 of Mycobacterium tuberculosis is excreted across the intima and EspB is also transported extracellularly through this secretory device on the intima.EspB is present in the resting culture Mycobacterium tuberculosis capsule layer can also be detected in the shaking culture of Mycobacterium tuberculosis by X-ray diffraction analysis , We analyzed the crystal structure of EspB and found different conformations of EspB compared with other homologous structures, that is, the EspB monomer can self-assemble into a regular structure of heptamer, Secretion, the discovery of heptameric conformations provides a clue to the role of EspB in the outward secreting of proteins by M. tuberculosis ie EspB has anchored in the M. tuberculosis capsule layer as a transporter for ESAT-6 Porous and possible.