Three-dimensional structure of human erythrocytic purine nucleoside phosphorylase at 3.2 A resolution.
Three-dimensional structure of human erythrocytic purine nucleoside phosphorylase at 3.2 A resolution.
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DOI：
10.2210/pdb2pnp/pdb
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发表时间：
1992-01
期刊：
影响因子：
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通讯作者：
S. Ealick;S. Rule;D. Carter;T. Greenhough;Y. Babu;W. Cook;J. Habash;J. Helliwell;J. Stoeckler;R. Parks
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文献类型：
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作者：
S. Ealick;S. Rule;D. Carter;T. Greenhough;Y. Babu;W. Cook;J. Habash;J. Helliwell;J. Stoeckler;R. Parks
用X射线衍射法测定了人红细胞嘌呤核苷磷酸化酶在3.2A分辨率下的三维结构。强度数据是使用来自英格兰达累斯伯里的同步辐射辐射源的辐射和振荡膜技术测量的。使用四个重原子衍生物的多重同象置换方法确定了物相，并使用溶剂平坦化技术进行了改进。嘌呤核苷磷酸化酶以三聚体的形式存在于晶体中，其亚基之间通过结晶学上的三重轴相连。每个亚基包含一个八链混合β-折叠和一个五链混合β-折叠，它们连接在一起形成扭曲的β-桶结构。这个核心贝塔结构的侧翼有七个α-螺旋，以一种新的折叠模式产生。活性部位位于三聚体内的亚基-亚基边界附近，其特征是底物类似物8-碘鸟嘌呤和5‘-碘福霉素B的结合，涉及来自一个亚基的七个不同片段和来自相邻亚基的另外一个短片段。在晶体中，磷酸盐结合位置可能被硫酸盐离子占据。嘌呤核苷磷酸化酶对鸟嘌呤、次黄嘌呤及其类似物的专一性可以根据活性部位上氢键供体和受体的排列来解释。
The three-dimensional structure of human erythrocytic purine nucleoside phosphorylase has been determined at 3.2 A resolution using x-ray diffraction data. Intensity data were measured using radiation from the Synchrotron Radiation Source, Daresbury, England, and oscillation film techniques. Phases were determined by using multiple isomorphous replacement methods with four heavy-atom derivatives and were improved using solvent flattening techniques. Purine nucleoside phosphorylase exists in the crystal as a trimer in which subunits are related by a crystallographic 3-fold axis. Each subunit contains an eight-stranded mixed beta-sheet and a five-stranded mixed beta-sheet which join to form a distorted beta-barrel structure. This core beta-structure is flanked by seven alpha-helices in a manner that generates a novel folding pattern. The active site, which was characterized from binding of the substrate analogs 8-iodoguanine and 5'-iodoformycin B, is located near the subunit-subunit boundary within the trimer and involves seven different segments from one subunit and an additional short segment from an adjacent subunit. In the crystal, the phosphate-binding site is probably occupied by a sulfate ion. The specificity of purine nucleoside phosphorylase for guanine, hypoxanthine, and their analogs can be explained on the basis of the arrangement of hydrogen bond donors and acceptors in the active site.