Copper binding to the prion protein: structural implications of four identical cooperative binding sites.
Copper binding to the prion protein: structural implications of four identical cooperative binding sites.
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DOI：
10.1073/pnas.96.5.2042
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发表时间：
1999-03
影响因子：
11.1
通讯作者：
J. H. Viles;F. Cohen;S. Prusiner;D. Goodin;P. Wright;H. Dyson
中科院分区：
文献类型：
--
作者：
J. H. Viles;F. Cohen;S. Prusiner;D. Goodin;P. Wright;H. Dyson
越来越多的证据支持朊病毒蛋白（PrP）在铜代谢中的功能作用。铜离子似乎在N末端附近的高度保守的八肽重复区（序列PHGGGWGQ）中与蛋白质结合。为了描绘的网站和模式的结合Cu（II）的PrP，铜的结合特性的肽的不同长度对应的2-，3-和4-octrepeat序列已被探测通过使用各种光谱技术。一个两个octarepeat肽结合一个单一的铜（II）离子与Kd约6 μ M，而四个octarepeat肽合作结合四个铜（II）离子。圆二色光谱表明一个独特的结构的octrepeat区域Cu（II）的结合。可见吸收，可见的圆二色谱，和电子自旋共振光谱表明，铜的配位球是相同的2，3，或4个octagrepeats，由一个正方形平面几何形状与三个氮配体和一个氧配体。与pH值的依赖性的Cu（II）的结合，质子NMR光谱表明，在每个octurepeat的组氨酸残基协调的Cu（II）离子。我们的工作模型的复杂的结构表明，组氨酸残基在连续的octrepeats桥接两个铜离子之间，与两个Nepsilon 2和Ndelta 1咪唑氮的每个组氨酸残基的协调和剩余的协调位点所占据的骨干酰胺氮和水分子。这种安排占合作性质的复杂的形成和明显的进化要求四个octurepeats在PrP。
Evidence is growing to support a functional role for the prion protein (PrP) in copper metabolism. Copper ions appear to bind to the protein in a highly conserved octapeptide repeat region (sequence PHGGGWGQ) near the N terminus. To delineate the site and mode of binding of Cu(II) to the PrP, the copper-binding properties of peptides of varying lengths corresponding to 2-, 3-, and 4-octarepeat sequences have been probed by using various spectroscopic techniques. A two-octarepeat peptide binds a single Cu(II) ion with Kd approximately 6 microM whereas a four-octarepeat peptide cooperatively binds four Cu(II) ions. Circular dichroism spectra indicate a distinctive structuring of the octarepeat region on Cu(II) binding. Visible absorption, visible circular dichroism, and electron spin resonance spectra suggest that the coordination sphere of the copper is identical for 2, 3, or 4 octarepeats, consisting of a square-planar geometry with three nitrogen ligands and one oxygen ligand. Consistent with the pH dependence of Cu(II) binding, proton NMR spectroscopy indicates that the histidine residues in each octarepeat are coordinated to the Cu(II) ion. Our working model for the structure of the complex shows the histidine residues in successive octarepeats bridged between two copper ions, with both the Nepsilon2 and Ndelta1 imidazole nitrogen of each histidine residue coordinated and the remaining coordination sites occupied by a backbone amide nitrogen and a water molecule. This arrangement accounts for the cooperative nature of complex formation and for the apparent evolutionary requirement for four octarepeats in the PrP.