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Structural Change of Ca^<++>-binding sites in Ca^<++>-binding protein by Solurion X-Ray Scattering

利用 Solurion X 射线散射法观察 Ca^< > 结合蛋白中 Ca^< > 结合位点的结构变化

基本信息

批准号：
60480488
负责人：
UEKI TATZUO
金额：
$ 4.35万
依托单位：
OSAKA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1985
资助国家：
日本
起止时间：
1985 至 1987
项目状态：
已结题

项目摘要

The contraction of muscle is controlled by the Ca^<++>ion concentration in the cell.The protein,that plays an important role in the initial stage of muscle contraction,is troponin C (MW-18,000).The present project is concerned with the structural changes induce by the binding of Ca^<++>ions to troponin C in solution,studied by solution X-ray scattering technique. The results are summarized below.1.The solution X-ray scattering from troponin C gives a distinct scattering profile in the moderate-angle region,in addition to the small-angle scattering.The profile changes as the binding of Ca^<++>ions to troponin C is controlled.2.The small-angle scattering from troponin C solution consists of two "Guinier regions"(in a plot of ln[I(S)]vs.S^2).This behavior is throughly described by a Dumbbell-shaped molecule model.The analysis of the scattering profile by a dumbbell-shaped model affords three important structural parameters;The radius of gyration of of troponin C molecule, Rg(molecule),radius of gyration of N-and C-terminal domain of molecule,Rg(domain)and the distance between the centers of domains,r_<n-c>.3.The Ca^<++>-free troponin C is described by the structural parameters,Rg(molecule)=27.8A,Rg(domain)=15.5A,r_<n-c>=46.3A.When the troponin C molecules bind with two/four Ca^<++>ions,the N-/C-terminal domain becomes more conpact,i.e.,Rg(domain)decrease from 15.5A-14.8A-14.6A. At the same time,the distance between the domains changes as 46.3A-37.3A-34.5A. This change is,in other words,the change of molecule itself,i.e.,the troponin C molecule becomes more compact as a whole.These results are in accord with the structure of troponin C molecule that carries two Ca^<++>ions in crystal.

肌钙蛋白C（Troponin C，MW-18，000）是肌肉收缩的起始蛋白，其收缩过程受细胞内Ca^<++>离子浓度的控制，本课题利用溶液X射线散射技术研究了Ca^<++>离子与Troponin C结合后引起的结构变化。结果总结如下：1.肌钙蛋白C的溶液X射线散射在中等角度区域给出了明显的散射轮廓，2.肌钙蛋白C溶液的小角散射由两个“Guinier区”组成，（In [I（S）]vs.S^2）.这种行为完全由哑铃形分子模型描述.用哑铃形模型分析散射分布提供了三个重要的结构参数;肌钙蛋白C分子的回旋半径Rg（分子）、N端和C端结构域的回旋半径Rg（结构域）和结构域中心之间的距离<n-c>r_3.无钙肌钙蛋白C的结构参数Rg（分子）= 27.8A，Rg（结构域）= 15.5A，r_4 <n-c>= 46.3A.当肌钙蛋白C分子与2/4个Ca^++离子结合时，N端和C端结构域变得更加紧密，即Rg（结构域）从15.5A-14.8A-14.6A降低。同时，畴间距离变化为46.3A-37.3A-34.5A。换句话说，这种变化是分子本身的变化，即，这与肌钙蛋白C分子在晶体中携带两个Ca^<++>离子的结构雅阁。