Wlodawer A, Bott R, Sjölin L
J Biol Chem. 1982 Feb 10;257(3):1325-32.
This paper describes the structure of bovine pancreatic ribonuclease A, refined by a restrained parameter least squares procedure at 2.0 A resolution, and rebuilt using computer graphics. The final agreement factor (formula see text) is 0.159. The positions of the 951 main chain atoms have been determined with an estimated accuracy of 0.17 A. In addition, the model includes a phosphate group in the active site and 176 waters, many of them with partial occupancy. The bond lengths in the refined structure of RNase A differ from the ideal values by an overall root mean square deviation of 0.022 A; the corresponding value for angle distances is 0.06 A. The root mean square deviation of planar atoms from ideality is 0.017 A, and root mean square deviation of the peptide torsion angles from 180 degrees is 3.4 degrees. The model is in good agreement with the final difference Fourier maps. Two active site histidines, His 12 and His 119, form hydrogen bonds to the phosphate ion. His 119 is also hydrogen bonded to the carboxyl of ASp 121 and His 12 to the carbonyl of Thr 45. The structure of the RNase A is very similar to that of RNase S, particularly in the active site region. The root mean square discrepancy of all atoms from residues 1 to 16 and 24 to 123 is 1.06 A and the root mean square discrepancy for the active site region is 0.6 A.
本文描述了牛胰核糖核酸酶A的结构，该结构通过约束参数最小二乘法在2.0埃分辨率下进行了精修，并使用计算机图形技术进行了重建。最终的拟合因子（公式见正文）为0.159。已确定951个主链原子的位置，估计精度为0.17埃。此外，该模型在活性位点包含一个磷酸基团和176个水分子，其中许多水分子占有率为部分占有率。核糖核酸酶A精修结构中的键长与理想值的总体均方根偏差为0.022埃；角度距离的相应值为0.06埃。平面原子与理想平面的均方根偏差为0.017埃，肽扭转角与180度的均方根偏差为3.4度。该模型与最终的差值傅里叶图吻合良好。两个活性位点组氨酸，即His 12和His 119，与磷酸根离子形成氢键。His 119还与Asp 121的羧基形成氢键，His 12与Thr 45的羰基形成氢键。核糖核酸酶A的结构与核糖核酸酶S的结构非常相似，特别是在活性位点区域。从残基1到16以及24到123的所有原子的均方根差异为1.06埃，活性位点区域的均方根差异为0.6埃。
