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

本研究主要针对参与金黄色葡萄球菌与宿主细胞黏附的蛋白质进行研究。本研究的最终目的是了解该细菌与宿主细胞的黏附机制，为药物设计奠定结构基础。在项目期间，通过X射线结晶学、小角X射线散射、圆二色谱和电子显微镜对被认为与心内膜炎有关的巨蛋白EbhA的结构进行了研究。首先，我们通过X射线结晶学确定了该分子的两个重复单元(EBH-R7-R8)的结构。然后，基于对小角X射线散射和CD光谱的研究，我们认为这些结构是串联的。此外，电子显微镜显示EBH-R10-19为约500A长的串，与所提出的结构一致。最后，我们根据X射线结构计算了该分子的螺旋参数，对整个EBH结构进行了模拟，结果表明EBH是一根长约3200A的弦。这些研究表明，EBH存在于金黄色葡萄球菌细胞表面，起到加强细胞骨架分子的作用。

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.