1.7 x射线结构周质的核糖大肠杆菌的受体。
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莫布雷SL,科尔磅
1.7 x射线结构周质的核糖大肠杆菌的受体。
J杂志。1992年5月5日,225 (1):155 - 75。
- PubMed ID
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1583688 (在PubMed]
- 文摘
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的x射线结构周质的核糖受体(结合蛋白)大肠杆菌(RBP)是解决3决议由多个同形的方法替换。交替循环的改装和细化导致27526年模型结构的r因子18.7%反射从7.5到1.7一项决议(96%的数据)。模型包含2228个non-hydrogen原子,包括所有271个残基的氨基酸序列,220溶剂原子和beta-D-ribose。蛋白质由两个高度相似的结构域,每一个都是由一个核心的平行β褶板两侧有阿尔法螺旋。这两个领域是相互关联的,一个几乎完美的2倍旋转轴,C末端的每个表的beta-strands指向中心的分子。三个短的氨基酸链(从对称相关的部分蛋白质)连接这两个领域,大概作为铰链允许相对运动功能域的重要的构象变化。两个水分子也是一种内在的铰链的一部分,允许灵活的结构至关重要。配体beta-D-ribose(吡喃糖形式)域之间的绑定,持有与侧链相互作用的内部循环。绑定网站量身定制,氢键、疏水性和立体效果形成紧密的绑定(0.1 microM核糖)和高特异性。有七个结合位点的残留物被指控(2天冬氨酸和精氨酸)和两个氢键。 The remaining hydrogen bonds are contributed by asparagine and glutamine residues. Three phenylalanine residues supply the hydrophobic component, packing against both faces of the sugar molecule. The arrangement of these hydrogen bonding and hydrophobic residues results in an enclosed binding site with the exact shape of the allowed sugar molecules; in the process of binding, the ligand loses all of its surface-accessible area. The sites of two mutations that affect the rate of folding of the ribose receptor are shown to be located near small cavities in the wild-type protein. The cavities thus allow the incorporation of the larger residues in the mutant proteins. Since these alterations would seriously affect the ability of the protein to build the first portion of the hydrophobic core in the first domain, it is proposed that this process is the rate-limiting step in folding of the ribose receptor.