Bu Z, Koide S, Engelman D M
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511, USA.
Protein Sci. 1998 Dec;7(12):2681-3. doi: 10.1002/pro.5560071223.
The crystal structure of a soluble form of Borrelia burgdorferi outer surface protein A (OspA) complexed with the Fab fragment of a monoclonal antibody has revealed an unusual structure that has a repetitive antiparallel beta topology with a nonglobular, single layer beta-sheet connecting the globular N- and C-terminal domains. Earlier NMR studies have shown that the local structure of OspA including the single layer beta-sheet is similar to the crystal structure. Here we report a small angle X-ray scattering (SAXS) study of the global conformation of OspA in solution. The radius of gyration (Rg) and the length distribution function (P(r)) of OspA measured by SAXS in solution are nearly identical to the calculated ones from the crystal structure, respectively. The NMR and SAXS experiments complement each other to show that OspA including the central single-layer beta-sheet is a stable structure in solution, and that the OspA crystal structure represents the predominant solution conformation of the protein.
与单克隆抗体的Fab片段复合的伯氏疏螺旋体外表面蛋白A（OspA）可溶性形式的晶体结构揭示了一种不寻常的结构，其具有重复的反平行β拓扑结构，带有连接球状N端和C端结构域的非球状单层β折叠。早期的核磁共振（NMR）研究表明，包括单层β折叠在内的OspA局部结构与晶体结构相似。在此，我们报告了一项关于溶液中OspA整体构象的小角X射线散射（SAXS）研究。通过SAXS在溶液中测量的OspA的回转半径（Rg）和长度分布函数（P(r)）分别与从晶体结构计算得到的结果几乎相同。NMR和SAXS实验相互补充，表明包括中央单层β折叠在内的OspA在溶液中是一种稳定结构，并且OspA晶体结构代表了该蛋白在溶液中的主要构象。
