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首页> 外文期刊>Acta crystallographica.Section D. Biological crystallography >Crystal structure reveals two alternative conformations in the active site of ribonuclease Sa2.
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Crystal structure reveals two alternative conformations in the active site of ribonuclease Sa2.

机译：晶体结构揭示了两个可选构象在核糖核酸酶的活性部位

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摘要

Three different strains of Streptomyces aureofaciens produce the homologous ribonucleases Sa, Sa2 and Sa3. The crystal structures of ribonuclease Sa (RNase Sa) and its complexes with mononucleotides have previously been reported at high resolution. Here, the structures of two crystal forms (I and II) of ribonuclease Sa2 (RNase Sa2) are presented at 1.8 and 1.5 A resolution. The structures were determined by molecular replacement using the coordinates of RNase Sa as a search model and were refined to R factors of 17.5 and 15.0% and R(free) factors of 21.8 and 17.2%, respectively. The asymmetric unit of crystal form I contains three enzyme molecules, two of which have similar structures to those seen for ribonuclease Sa, with Tyr87 at the bottom of their active sites. In the third molecule, Tyr87 has moved substantially: the CA atom moves almost 5 A and the OH of the side chain moves 10 A, inserting itself into the active site of a neighbouring molecule at a similar position to that observed for the nucleotide base in RNase Sa complexes. The asymmetric unit of crystal form II contains two Sa2 molecules, both of which are similar to the usual Sa structures. In one molecule, two main-chain conformations were modelled in the alpha-helix. Finally, a brief comparison is made between the conformations of the Sa2 molecules and those of 34 independent molecules taken from 20 structures of ribonuclease Sa and two independent molecules taken from two structures of ribonuclease Sa3 in various crystal forms.
机译：三个不同的链霉菌属的菌株aureofaciens产生相应的核糖核酸酶Sa Sa2 Sa3。核糖核酸酶Sa(核糖核酸酶Sa)及其复合物单核苷酸曾被报道高分辨率。晶体形式(I和II)的核糖核酸酶Sa2(核糖核酸酶Sa2)在1.8和1.5决议。分子替换使用的坐标核糖核酸酶Sa搜索模型和精制R因素17.5和15.0%,R(免费)的因素分别为17.2%和21.8。我包含三个酶的晶体形式分子,其中两个有类似的结构那些见过的核糖核酸酶Sa, Tyr87他们活跃网站的底部。分子,Tyr87已经大大:CA原子移动几乎5的哦链移动10,将自己插入到邻近分子的活性部位能够观察到的相似核糖核酸酶核苷酸基地Sa复合物。不对称单元二包含两个晶体形式Sa2分子,都是类似的通常的公司结构。主链构象被模仿阿尔法螺旋。Sa2分子的构象之间和来自34个独立分子20核糖核酸酶Sa和两个结构独立分子来自两种结构各晶体的核糖核酸酶Sa3形式。

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