Gao B, Ma X Q, Wang Y P, Chen S Z, Wu S, Dong Y C
Institute of Biophysics, Academia Sinica, Beijing, PRC.
Sci China B. 1994 Jan;37(1):59-73.
An X-ray reflection data set of the orthorhombic crystal of Trichosanthin (TCS) at 1.73 A resolution had been collected using the area detector. We determined TCS crystal structure by the molecular replacement method using the data of the known alpha-momocharin model and TCS intensities, and then TCS structure refinement at 1.73 A resolution was performed with the restrained least-squares refinement. A final R-factor of 0.186 was obtained with a model obeying standard geometry within 0.013 A in bond lengths and 2.48 degrees in bond angles. The final model contains 133 solvent molecules in the asymmetric unit. This paper gives a detailed description of TCS molecule structure, temperature factors, hydrogen bonds, bound water, the distribution of conserved residues and the interactions between the TCS molecules. The hydrogen bond between the hydroxyl group of conserved residue 14Tyr and O157 plays an important role in maintaining the active site conformation. Conserved residue 160Glu and its conformation at the active site play a key role in the catalytic activity.
利用面探测器收集了分辨率为1.73 Å的天花粉蛋白（TCS）正交晶体的X射线反射数据集。我们使用已知的α-苦瓜素模型数据和TCS强度，通过分子置换法确定了TCS晶体结构，然后采用约束最小二乘精修对分辨率为1.73 Å的TCS结构进行精修。最终获得的R因子为0.186，模型的键长在0.013 Å内符合标准几何结构，键角在2.48°内符合标准几何结构。最终模型在不对称单元中包含133个溶剂分子。本文详细描述了TCS分子结构、温度因子、氢键、结合水、保守残基的分布以及TCS分子之间的相互作用。保守残基14Tyr的羟基与O157之间的氢键在维持活性位点构象方面起重要作用。保守残基160Glu及其在活性位点的构象在催化活性中起关键作用。
