G protein subtype specificity of rhodopsin intermediates metarhodopsin Ib and metarhodopsin II.
G protein subtype specificity of rhodopsin intermediates metarhodopsin Ib and metarhodopsin II.
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视紫红质中间体变视紫红质 Ib 和变视紫红质 II 的 G 蛋白亚型特异性。
DOI：
10.1111/j.1751-1097.2008.00396.x
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
T. Yamashita and Y. Shichida
中科院分区：
文献类型：
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作者：
T. Morizumi;N. Kimata;A. Terakita;Y. Imamoto;T. Yamashita and Y. Shichida
视紫红质是G蛋白偶联受体家族的成员之一，其可以在光子吸收时催化视网膜G蛋白转导素（Gt）上的GDP-GTP交换反应。至少有两种中间状态，meta-Ib和meta-II，它们表现出与GT的直接相互作用。Meta-Ib与GDP结合的GT结合，而meta-II与没有核苷酸的GT形成复合物，这表明meta-Ib是最初与GT相互作用的状态。在这里，我们研究了meta-Ib是否表现出与G蛋白类似于meta-II的特异性相互作用，通过检测Meta-Ib和Meta-II与Giα及其C末端11个氨基酸被Goα、Gqα和Gsα取代的突变体的结合效率。Meta对Gtα C末端11个氨基酸的亲和力与Giα及其Goα C末端11个氨基酸的突变体相似，而Meta对Goα C末端11个氨基酸的Giα突变体C末端11个氨基酸的亲和力约为Gtα和Giα的一半。两种中间体均对含有Gqα和Gsα C末端11个氨基酸的Giα突变体无亲和力。这些结果表明，Meta-Ib是与Meta-II一样表现出与G蛋白特异性相互作用的状态，尽管Meta-Ib与Meta-II相比表现出略微宽松的结合选择性。
Rhodopsin is one of the members of the G protein‐coupled receptor family that can catalyze a GDP–GTP exchange reaction on the retinal G protein transducin (Gt) upon photon absorption. There are at least two intermediate states, meta‐Ib and meta‐II, which exhibit direct interaction with Gt. Meta‐Ib binds to GDP‐bound Gt, while meta‐II forms a complex with Gt having no nucleotide, suggesting that meta‐Ib is a state that initially interacts with Gt. Here we investigated whether or not meta‐Ib exhibits specific interaction with G protein similar to meta‐II, by examining the binding efficiencies of meta‐Ib and meta‐II to Giα and its mutants whose C‐terminal 11 amino acids were replaced with those of Goα, Gqα and Gsα. The affinity of meta‐Ib to the C‐terminal 11 amino acids of Gtα was similar to those of Giα and its mutant with Goα’s C‐terminal 11 amino acids, whereas meta‐II exhibited affinity to the C‐terminal 11 amino acids of Giα mutant with Goα’s C‐terminal 11 amino acids about half of what was seen for Gtα and Giα. Both intermediates exhibited no affinity to the Giα mutants containing the C‐terminal 11 amino acids of Gqα and Gsα. These results suggested that meta‐Ib is the state that exhibits specific interaction with G protein as meta‐II does, although meta‐Ib exhibits a slightly lenient binding selectivity compared to that of meta‐II.