Allen S C, Acharya K R, Palmer K A, Shapiro R, Vallee B L, Scheraga H A
School of Biology and Biochemistry, University of Bath, Claverton Down, UK.
J Protein Chem. 1994 Oct;13(7):649-58. doi: 10.1007/BF01890464.
The three-dimensional structure of human angiogenin has been determined by X-ray crystallography and is compared here with an earlier model which predicted its structure, based on the homology of angiogenin with bovine pancreatic ribonuclease A. Comparison of the predicted model and crystal structure shows that the active-site histidine residues and the core of the angiogenin molecule, including most of the beta-strands and alpha-helices, were predicted reasonably well. However, the structure of the surface loop regions and residues near the truncated C-terminus differs significantly. The C-terminal segment includes the active-site residues Asp-116, Gln-117, and Ser-118; Gln-117 in particular has been shown to be important in affecting the ribonucleolytic activity of angiogenin. Also, the orientation of one helix in the model differed from the orientation observed experimentally by about 20 degrees, resulting in a large displacement of this chain segment. The difficulty encountered in predicting the surface loop regions has led to a new algorithm [Palmer and Scheraga (1991), J. Comput. Chem., 12, 505-526; (1992), J. Comput. Chem., 13, 329-350] for predicting the conformations of surface loops.
人血管生成素的三维结构已通过X射线晶体学确定，并在此与早期基于血管生成素与牛胰核糖核酸酶A的同源性预测其结构的模型进行比较。预测模型与晶体结构的比较表明，活性位点组氨酸残基以及血管生成素分子的核心，包括大部分β链和α螺旋，预测得相当不错。然而，表面环区和截短的C末端附近残基的结构差异显著。C末端片段包括活性位点残基Asp-116、Gln-117和Ser-118；特别是Gln-117已被证明在影响血管生成素的核糖核酸酶活性方面很重要。此外，模型中一个螺旋的方向与实验观察到的方向相差约20度，导致该链段有较大位移。预测表面环区时遇到的困难促使人们开发了一种新算法[帕尔默和谢拉加（1991年），《计算化学杂志》，12卷，505 - 526页；（1992年），《计算化学杂志》，13卷，329 - 350页]来预测表面环的构象。
