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首页> 外文期刊>Biochemistry >Structural and Dynamic Study of the Tetramerization Region of Non-Erythroid α-Spectrin: A Frayed Helix Revealed by Site-Directed Spin Labeling Electron Paramagnetic Resonance
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Structural and Dynamic Study of the Tetramerization Region of Non-Erythroid α-Spectrin: A Frayed Helix Revealed by Site-Directed Spin Labeling Electron Paramagnetic Resonance

机译：非类红体α-Spectrin四聚体区域的结构和动力学研究：通过定点自旋标记电子顺磁共振显示磨损的螺旋。

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摘要

The N-terminal region of α-spectrin is responsible for its association with β-spectrin in a heterodimer, forming functional tetramers. Non-erythroid α-spectrin (αII-spectrin) has a significantly higher association affinity for β-spectrin than the homologous erythroid α-spectrin (αI-spectrin). We have previously determined the solution structure of the N-terminal region of αI-spectrin by NMR methods, but currently no structural information is available for αII-spectrin. We have used cysteine scanning, spin labeling electron paramagnetic resonance (EPR), and isothermal titration calorimetry (ITC) methods to study the tetramerization region of αII-spectrin. EPR data clearly show that, in αII-spectrin, the first nine N-terminal residues were unstructured, followed by an irregular helix (helix C′), frayed at the N-terminal end, but rigid at the C-terminal end, which merges into the putative triple-helical structural domain. The region corresponding to the important unstructured junction region linking helix C′ to the first structural domain in αI-spectrin was clearly structured. On the basis of the published model for aligning helices A′, B′, and C′, important interactions among residues in helix C′ of αI- and αII-spectrin and helices A′ and B′ of βI- and βII-spectrin are identified, suggesting similar coiled coil helical bundling for spectrin I and II in forming tetramers. The differences in affinity are likely due to the differences in the conformation of the junction regions. Equilibrium dissociation constants of spin-labeled αII and βI complexes from ITC measurements indicate that residues 15, 19, 37, and 40 are functionally important residues in αII-spectrin. Interestingly, all four corresponding homologous residues in αI-spectrin (residues 24, 28, 46, and 49) have been reported to be clinically significant residues involved in hematological diseases.
机译：α-血影蛋白的N末端区域负责与异二聚体中的β-血影蛋白缔合，形成功能性四聚体。非类胡萝卜素α-血影蛋白（αII-血影蛋白）对β-血影蛋白的结合亲和力明显高于同源的类红血球α-血影蛋白（αI-血影蛋白）。我们之前已经通过NMR方法确定了αI-血影蛋白N末端区域的溶液结构，但是目前尚无关于αII-血影蛋白的结构信息。我们已经使用半胱氨酸扫描，自旋标记电子顺磁共振（EPR）和等温滴定量热（ITC）方法来研究αII-血影蛋白的四聚化区域。 EPR数据清楚地表明，在αII-血影蛋白中，前9个N末端残基是无结构的，随后是不规则的螺旋（螺旋C'），在N末端呈磨损状，但在C末端呈刚性，这合并到假定的三螺旋结构域中。清楚地构造了与将螺旋C'连接至αI-血影蛋白的第一结构域的重要的非结构化连接区域相对应的区域。在公开的排列螺旋A'，B'和C'的模型的基础上，αI-和αII-血影蛋白的螺旋C'中的残基与βI-和βII-血影蛋白的螺旋A'和B'中的重要相互作用为鉴定，表明在形成四聚体时，血影蛋白I和II具有相似的盘绕螺旋螺旋束。亲和力的差异可能是由于结区构象的差异。根据ITC测量，自旋标记的αII和βI复合物的平衡解离常数表明，残基15、19、37和40是αII-血影蛋白中功能上重要的残基。有趣的是，据报道αI-血影蛋白中所有四个相应的同源残基（残基24、28、46和49）是涉及血液病的临床上重要的残基。

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  • 来源
    《Biochemistry》 |2009年第1期|p.206-215|共10页
  • 作者

    Qufei Li and L. W.-M. Fung;

  • 作者单位

    Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, MC 111, Chicago, Illinois 60607;

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