Structure of bovine pancreatic trypsin inhibitor. Results of joint neutron and X-ray refinement of crystal form II.
Structure of bovine pancreatic trypsin inhibitor. Results of joint neutron and X-ray refinement of crystal form II.
复制标题
牛胰腺胰蛋白酶抑制剂的结构。
DOI：
10.2210/pdb5pti/pdb
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发表时间：
1984
影响因子：
5.6
通讯作者：
L. Sjölin
中科院分区：
文献类型：
--
作者：
A. Wlodawer;J. Walter;R. Huber;L. Sjölin
通过 X 射线和中子数据的联合细化，研究了牛胰蛋白酶抑制剂 II 型晶体的结构。最终模型的晶体学 R 因子对于扩展至 1 A 分辨率的 X 射线数据为 0.200，对于 1.8 A 中子数据为 0.197。该模型受到强烈约束，键长与理想值的均方根 (r.m.s.) 偏差为 0.020 A r.m.s.，键长与理想值的偏差为 0.019 A r.m.s.。平面群偏离平面性。所得结构与晶型I非常相似（主链原子均方根偏差为0.40A）；然而，在链条的特定区域观察到较大的偏差。在两个模型中，63 个有序水分子中有 20 个占据相似的位置（偏差小于 1 A）。将晶体浸泡在 pH 8.2 的氘化母液中三个月后，发现 11 个酰胺氢被保护免于交换。它们的位置与二维核磁共振获得的结果非常一致，但晶态下的交换率要低得多。
The structure of form II crystals of bovine pancreatic trypsin inhibitor has been investigated by joint refinement of X-ray and neutron data. Crystallographic R factors for the final model were 0.200 for the X-ray data extending to 1 A resolution and 0.197 for the 1.8 A neutron data. This model was strongly restrained, with 0.020 A root-mean-square (r.m.s.) departure of bond lengths from their ideal values and 0.019 A r.m.s. departure of planar groups from planarity. The resulting structure was very similar to that of crystal form I (r.m.s. deviation for main chain atoms was 0.40 A); nevertheless larger deviations were observed in particular regions of the chain. Twenty out of 63 ordered water molecules occupy similar positions (deviation less than 1 A) in both models. Eleven amide hydrogens were found to be protected from exchange after three months of soaking the crystals in deuterated mother liquor at pH 8.2. Their locations were in excellent agreement with the results obtained by two-dimensional nuclear magnetic resonance, but the rates of exchange are much lower in the crystalline state.