Refinement of the crystal structure of wheat germ agglutinin isolectin 2 at 1.8 A resolution.
Refinement of the crystal structure of wheat germ agglutinin isolectin 2 at 1.8 A resolution.
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在 1.8 A 分辨率下精修麦芽凝集素异凝集素 2 的晶体结构。
DOI：
10.1016/0022-2836(87)90678-4
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发表时间：
1987
影响因子：
5.6
通讯作者：
Wright,CS
中科院分区：
文献类型：
--
作者：
Wright,CS
麦胚凝集素异凝集素2的晶体结构已通过Hendrickson和Konnert（1980）的约束最小二乘法进行了优化。C2晶体的不对称单元包含两个化学性质相同的原异构体，它们通过非晶体学的2倍螺旋操作而相互关联。共2290个蛋白质原子和186个有序水位点，最终R因子为0.179，平均B值为21.6 σ 2，使用分辨率范围为8 - 1.8 σ的反射总数的54%（15，601），Fo> 3σ（Fo）。最终模型符合立体化学正确的键距和键角，具有均方根（r.m.s.）值分别为0.018 °和3.3 °。根据Luzzati图估计该模型的精度为0.20 μ m。在两个独立的启动子中的主链原子位置，指定为I和II，与r.m.s.偏差为0.30 π（所有原子为0.58 π），表明骨架构象相同。最大的差异是在柔性表面残留物。在第41位氨基酸序列（Ser）中检测到一个错误，该错误令人满意地作为Trp进行了改进。在精制过程中残基A171的电子密度损失表明该C-末端残基的无序或不存在。残基结构域（A、B、C和D），根据二面角、骨架氢键长度和CA原子位置进行分析。根据所有这些标准，发现四个结构域非常相似，并且它们的CA原子的叠加产生r.m.s.对于六种可能的比较，距离范围从0.36到0.72 μ m。大的偏差（> 1.0kb）仅见于连接相邻结构域的五个残基片段以及N和C末端。精细化还允许对不同晶格环境中的两个独特糖结合位点（称为“初级”和“次级”位点）中的每一个进行严格检查。虽然这些位点中的每个位点（Y 73，Y159）中的基本酪氨酰侧链假定精确的取向以与糖配体的N-乙酰基甲基进行最佳疏水接触，但发现参与氢键的侧链（S62，E115;和S148，D29）相对灵活，并且能够使其构象适应环境的变化。在不同的环境中，这些结合位点中存在的有序水结构并不完全相似。此外，在独立的环境中，对二聚化和晶格稳定很重要的分子间相互作用以及蛋白质-溶剂缔合也被检查和比较。
The crystal structure of wheat germ agglutinin isolectin 2 has been refined by the restrained least-squares method of Hendrickson & Konnert (1980). The asymmetric unit of theC2 crystals contains two chemically identical protomers related by a non-crystallographic 2-fold screw operation. A total of 2290 protein atoms and 186 ordered water sites refined to a finalR-factor of 0.179 and an averageB-value of 21.6Å2, using 54% (15,601) of the total possible number of reflections in the resolution range 8 to 1.8ÅwithFo> 3σ(Fo). The final model conforms to stereochemically correct bond distances and angles with root-mean-square (r.m.s.) values of 0.018Åand 3.3 °, respectively. Accuracy of this model is estimated to be 0.20Åon the basis of a Luzzati plot. Main-chain atomic positions in the two independent promoters, designated I and II, agree with an r.m.s. deviation of 0.30Å(0.58Åfor all atoms), indicating identical backbone conformation. The largest discrepancies are seen at flexible surface residues. One error was detected in the amino acid sequence at position 41 (Ser), which refined satisfactorily as a Trp. Loss of electron density for residue A171 during the course of refinement suggests either disorder or absence of this C-terminal residue. residue domains (A, B, C and D), was analyzed in terms of dihedral angles, backbone hydrogen bond lengths and CA-atom positions. The four domains were found to be very similar according to all these criteria and superposition of their CA-atoms yielded r.m.s. distances ranging from 0.36 to 0.72Åfor the six possible comparisons. Large deviations (> 1.0Å) are only seen in the five-residue segments that link adjacent domains and at the N and C termini.Refinement has also allowed critical examination of each of the two unique sugar binding sites, referred to as “primary” and “secondary” sites, in different lattice environments. While the essential tyrosyl side-chain in each of these sites (Y73, Y159) assumes precise orientation for optimum hydrophobic contact with theN-acetyl methyl group of the sugar ligand, side-chains involved in hydrogen bonds (S62, E115; and S148, D29) were found to be relatively flexible and able to adapt their conformation to changes in environment. Ordered water structure present in these binding sites is not completely analogous in the different environments.In addition, intermolecular interactions as well as protein-solvent association, important for dimerization and stabilization of the crystal lattice, have been examined and compared in the independent environments.
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影响因子：
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DOI：
--
发表时间：
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期刊：
影响因子：
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影响因子：
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影响因子：
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影响因子：
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