Perkins S J, Ashton A W, Boehm M K, Chamberlain D
Department of Biochemistry and Molecular Biology, Royal Free Hospital School of Medicine, London, UK.
Int J Biol Macromol. 1998 Feb;22(1):1-16. doi: 10.1016/s0141-8130(97)00088-3.
Molecular structures can be extracted from solution scattering analyses of multidomain or oligomeric proteins by a new method of constrained automated scattering curve fits. Scattering curves are calculated using a procedure tested by comparisons of crystal structures with experimental X-ray and neutron data. The domains or subunits in the protein of interest are all represented by atomic coordinates in order to provide initial constraints. From this starting model, hundreds or thousands of different possible structures are computed, from each of which a scattering curve is computed. Each model is assessed for steric overlap, radii of gyration and R-factors in order to leave a small family of good fit models that corresponds to the molecular structure of interest. This method avoids the tedium of curve fitting by hand and error limits on the ensuing models can be described. For single multidomain proteins, the key constraint is the correct stereochemical connections between the domains in all the models. Successful applications to determine structures are summarised for the Fab and Fc fragments in immunoglobulin G, the three domain pairs in the Fc subunit of immunoglobulin E and the seven, domains in carcinoembryonic antigen. For oligomeric proteins, the key constraint is provided by symmetry and successful analyses were performed for the association of the monomers of the bacterial amide sensor protein AmiC to form trimers and pentameric serum amyloid P component to form decameric structures. The successful analysis of the heterodimeric complex of tissue factor and factor VIIa required the use of constraints provided from biochemical data. The outcome of these analyses is critically appraised, in particular the biological significance of structures determined by these solution scattering curve fits.
通过一种新的受限自动散射曲线拟合方法，可以从多结构域或寡聚蛋白的溶液散射分析中提取分子结构。使用通过将晶体结构与实验X射线和中子数据进行比较而测试的程序来计算散射曲线。感兴趣的蛋白质中的结构域或亚基均由原子坐标表示，以提供初始约束。从这个起始模型开始，计算出数百或数千种不同的可能结构，并从每种结构中计算出一条散射曲线。对每个模型进行空间重叠、回转半径和R因子评估，以留下一小部分与感兴趣的分子结构相对应的拟合良好的模型。该方法避免了手工拟合曲线的繁琐，并且可以描述后续模型的误差范围。对于单个多结构域蛋白，关键约束是所有模型中各结构域之间正确的立体化学连接。总结了该方法在确定免疫球蛋白G的Fab和Fc片段、免疫球蛋白E的Fc亚基中的三个结构域对以及癌胚抗原中的七个结构域的结构方面的成功应用。对于寡聚蛋白，关键约束由对称性提供，并且对细菌酰胺传感器蛋白AmiC的单体缔合形成三聚体以及五聚体血清淀粉样蛋白P成分形成十聚体结构进行了成功分析。组织因子和因子VIIa异二聚体复合物的成功分析需要使用生化数据提供的约束。对这些分析的结果进行了严格评估，特别是通过这些溶液散射曲线拟合确定的结构的生物学意义。
