Weiergräber Oliver H, Senin Ivan I, Zernii Eugene Yu, Churumova Valeriya A, Kovaleva Nadezhda A, Nazipova Aliya A, Permyakov Sergei E, Permyakov Eugene A, Philippov Pavel P, Granzin Joachim, Koch Karl-Wilhelm
Institut für Biologische Informationsverarbeitung (IBI-2, Biologische Strukturforschung), Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany.
J Biol Chem. 2006 Dec 8;281(49):37594-602. doi: 10.1074/jbc.M603700200. Epub 2006 Oct 2.
Recoverin is a Ca(2+)-regulated signal transduction modulator expressed in the vertebrate retina that has been implicated in visual adaptation. An intriguing feature of recoverin is a cluster of charged residues at its C terminus, the functional significance of which is largely unclear. To elucidate the impact of this segment on recoverin structure and function, we have investigated a mutant lacking the C-terminal 12 amino acids. Whereas in myristoylated recoverin the truncation causes an overall decrease in Ca(2+) sensitivity, results for the non-myristoylated mutant indicate that the truncation primarily affects the high affinity EF-hand 3. The three-dimensional structure of the mutant has been determined by x-ray crystallography. In addition to significant changes in average coordinates compared with wild-type recoverin, the structure provides strong indication of increased conformational flexibility, particularly in the C-terminal domain. Based on these observations, we propose a novel role of the C-terminal segment of recoverin as an internal modulator of Ca(2+) sensitivity.
恢复蛋白是一种在脊椎动物视网膜中表达的钙（Ca(2+)）调节信号转导调节剂，与视觉适应有关。恢复蛋白的一个有趣特征是其C末端有一簇带电荷的残基，其功能意义在很大程度上尚不清楚。为了阐明该片段对恢复蛋白结构和功能的影响，我们研究了一个缺失C末端12个氨基酸的突变体。在肉豆蔻酰化的恢复蛋白中，截短导致Ca(2+)敏感性总体下降，而非肉豆蔻酰化突变体的结果表明，截短主要影响高亲和力的EF手型结构域3。该突变体的三维结构已通过X射线晶体学确定。与野生型恢复蛋白相比，除了平均坐标有显著变化外，该结构还强烈表明构象灵活性增加，尤其是在C末端结构域。基于这些观察结果，我们提出恢复蛋白C末端片段作为Ca(2+)敏感性的内部调节剂的新作用。
