STRUCTURE OF FORM-III CRYSTALS OF BOVINE PANCREATIC TRYPSIN-INHIBITOR
STRUCTURE OF FORM-III CRYSTALS OF BOVINE PANCREATIC TRYPSIN-INHIBITOR
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DOI：
10.1016/0022-2836(87)90294-4
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发表时间：
1987-12-05
影响因子：
5.6
通讯作者：
WOODWARD, C
中科院分区：
文献类型：
--
作者：
WLODAWER, A;NACHMAN, J;WOODWARD, C
牛胰蛋白酶抑制剂的结构已以新晶型 III 的形式得到解析。该晶体属于P21212空间群，a=55.2°A，b=38.2°A，c=24.05°A。根据抑制剂晶型I和II的坐标，通过分子置换求解结构，X射线数据延伸至1.7°A。用于约束最小二乘精炼。最终的 R 因子为 0.16，键合距离与理想值的偏差为 0.020°ANG。晶型III和I的坐标为0.47°A，而晶型II和III之间的差异为0.39°A。这些偏差比预期的实验误差大约3倍，表明三种晶型之间存在真正的差异。两个残基（Arg39 和 Asp50）用其侧链的两个位置进行建模。最终模型包括 73 个水分子和一个与蛋白质结合的磷酸基团。迄今为止研究的所有三种晶体形式中，十六个水分子占据大致相同的位置，表明它们与蛋白质分子密切相关。温度因素也显示出三种晶型之间的高度相关性。
The structure of bovine pancreatic trypsin inhibitor has been solved in a new crystal form III. The crystals belong to space group P21212 with a = 55.2 .ANG., b = 38.2 .ANG., c = 24.05 .ANG.. The structure was solved on the basis of co-ordinates of forms I and II of the inhibitor by molecular replacement, and the X-ray data extending to 1.7 .ANG. were used in a restrained least-squares refinement. The final R factor was 0.16, and the deviation of bonded distances from ideality was 0.020 .ANG.. Root-mean-square discrepancy between C.alpha. co-ordinates of forms III and I are 0.47 .ANG., whilst between forms II and III the discrepancy is 0.39 .ANG.. These deviations are about a factor of 3 larger than the expected experimental errors, showing that true differences exist between the three crystal forms. Two residues (Arg39 and Asp50) were modeled with two positions for their side-chains. The final model includes 73 water molecules and one phosphate group bound to the protein. Sixteen water molecules occupy approximately the same positions in all three crystal forms studied to date, indicating their close association with the protein molecule. Temperature factors also show a high degree of correlation between the three crystal forms.