Structural and functional analysis of a cell wall-associated giant protein EbhA from Staphylococcus aureus

本研究的重点是参与金黄色葡萄球菌与宿主细胞粘附的蛋白。本研究的最终目的是了解该细菌与宿主细胞的粘附机制，为药物设计奠定结构基础。项目期间，通过x射线晶体学、x射线小角散射、CD谱和电子显微镜研究了一种被认为参与心内膜炎的巨蛋白EbhA的结构。首先，我们用x射线晶体学分析了该分子的两个重复单元（Ebh-R7-R8）的结构。然后，基于小角x射线散射和CD光谱的研究，我们提出了这些结构是串联连接的。电镜分析表明，ehb - r10 -19为长度约为500A的串，与本文提出的结构一致。最后，我们根据x射线结构计算了该分子的螺旋参数，模拟了整个Ebh结构，结果表明Ebh是长度约为3200 A的字符串。这些研究表明，Ebh位于金黄色葡萄球菌细胞表面，发挥“骨架分子”的作用，加固细胞。

This research focused on the protein involved in the adhesion of Staphylococcus aureus to the host cell. The final goal of this research is to understand the adhesion mechanism of this bacterium to the host cell and to establish the structural basis for the drug design. During the project period, the structure of a giant protein EbhA, which was thought to be involved in the endocarditis, was investigated by the X-ray crystallography, small angle X-ray scattering, CD spectroscopy and electron microscopy. First, we elucidated the structure of the two repeating units (Ebh-R7-R8) of this molecule by the X-ray crystallography. Then, based on the studies of the small angle X-ray scattering and CD spectrometry, we proposed that these structures are connected tandem. Furthermore, the electron microscopy showed that the Ebh-R10-19 is the string of about 500A in length which is consistent with the proposed structure. Finally, we simulated the whole Ebh structure by calculating the helical parameters of this molecule based on the X-ray structure, which showed that Ebh is the string of about 3200 A in length. These studies suggest that Ebh is on the surface of the Staphylococcus aureus cell and plays the role as "skeleton molecule" to reinforce the cell.