Lipid-protein interactions mediate the photochemical function of rhodopsin.
Lipid-protein interactions mediate the photochemical function of rhodopsin.
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脂质-蛋白质相互作用介导视紫红质的光化学功能。
DOI：
10.1021/bi00417a041
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发表时间：
1988
期刊：
影响因子：
2.9
通讯作者：
Brown,MF
中科院分区：
文献类型：
--
作者：
Wiedmann,TS;Pates,RD;Beach,JM;Salmon,A;Brown,MF
帝莫西·S. Robert D.作者：James M.海滩，阿米尔鲑鱼，和迈克尔F。Brown*，§ Department of Chemistry，University of Virginia，Charlottesville，Virginia 22901 Received December 18，1987; Revised Mandarin pt Received April 13，1988摘要：我们已经研究了重组膜的分子特征，这些特征对于视紫红质的光化学功能是必要的。在28 ℃和pH7.0下，在25%±3%漂白闪光之后，将视紫红质I到视紫红质II的光瞬变的幅度用作光化学活性的标准。天然活性的视紫红质可以重建与总脂杆外段膜的提取物，表明该蛋白质是最低限度地扰动的重建协议。视紫红质的光化学活性增强磷脂酰乙醇胺头基团和二十二碳六烯酰基（22：6 3）酰基链。含有50 mol%二十二碳六烯酰基链的磷脂酰乙醇胺和磷脂酰胆碱的等摩尔混合物导致最佳的光化学功能。这些结果表明，在视觉过程中的杆外节脂质的头基和酰基链组成的重要性。提取的杆脂质和那些脂质混合物有利于构象变化从metarhodopsin I到II可以经历层状（LJ）到倒六边形（Hn）相变接近生理温度。视紫红质与接近La至Hn（或立方）相界的膜脂质的相互作用因此可能导致影响与视觉功能相关的蛋白质的构象状态的能量学的性质。视紫红质是一种位于视杆细胞外节（ROS）1盘膜中的完整蛋白质，其视网膜发色团的顺式至反式光异构化引发视觉过程（Wald，1968）。提供了由杆产生神经冲动的当前范例的事件可以总结如下（Kiihn，1984; Chabre，1985）。视杆细胞质膜响应于视紫红质吸收光子的超极化由细胞内第二信使介导（米勒和尼科尔，1979; Yoshikami等人，1980年）。光活化的视紫红质（R*）分子与信号转导G蛋白相互作用，导致GTP与GDP的交换放大、磷酸二酯酶活化和环GMP的水解（Fung & Stryer，1980; Kiihn等人，1981;刘易斯等人，1984; Kiihn，1984; Chabre，1985; Kohl& Hofmann，1987）。环GMP依赖性质膜通道的关闭（Matesic & Liebman，1987）导致超极化。视紫红质的光活化通常被认为涉及与其前体视紫红质I（MI）处于平衡的视紫红质II（MII）光中间体（Kiihn，1984; Chabre，1985; Kohl & Hofmann，1987）。MI-MII跃迁包括视紫红质吸收最大值从478 nm到380 nm的位移，发生在视觉光传导的毫秒时间尺度上，并且已知涉及一个由美国国立卫生研究院资助EY 03754，
Timothy S. Wiedmann,* Robert D. Pates, James M. Beach, Amir Salmon, and Michael F. Brown*, § Department of Chemistry, University of Virginia, Charlottesville, Virginia 22901 Received December 18, 1987; Revised Manuscript Received April 13, 1988 abstract: We have investigated the molecular features of recombinant membranes that are necessary for the photochemical function of rhodopsin. The magnitude of the metarhodopsin I to metarhodopsin II phototransient following a 25%±3% bleaching flash was used as a criterion of photochemical activity at 28 C and pH 7.0. Nativelike activity of rhodopsin can be reconstituted with an extract of totallipids from rod outer segment membranes, demonstrating that the protein is minimally perturbed by the reconstitution protocol. Rhodopsin photochemical activity is enhanced by phosphatidylethanolamine head groups and docosahexaenoyl (22: 6 3) acyl chains. An equimolar mixture of phosphatidylethanolamine and phos-phatidylcholine containing 50 mol% docosahexaenoyl chains results inoptimal photochemical function. These results suggest the importance of both the head-group and acyl chain composition of the rod outer segment lipids in the visual process. The extracted rod lipids and those lipid mixtures favoring the con-formational change from metarhodopsin I to II can undergo lamellar (LJ to inverted hexagonal (Hn) phase transitions near physiological temperature. Interaction of rhodopsin with membrane lipids close to a La to Hn (or cubic) phase boundary may thus lead to properties which influence the energetics of conformational states of the protein linked to visual function. e process of vision is initiated by cis to trans photoisomerization of the retinal chromophore of rhodopsin, an integral protein located in the disk membranes of the rod outer segment (ROS) 1 (Wald, 1968). The events that provide a current paradigm for generation of a nerve impulse by the rod can be summarized as follows (Kiihn, 1984; Chabre, 1985). Hy-perpolarization of the rod plasma membrane in response to absorption of a photon by rhodopsin is mediated by an in-tracellular second messenger (Miller &Nicol, 1979; Yoshikami et al., 1980). The photoactivated rhodopsin (R*) molecules interactwith a signal-transducing G-protein, leading to amplified exchange of GTP for GDP, phosphodiesterase activation, and hydrolysis of cyclic GMP (Fung & Stryer, 1980; Kiihn et al., 1981; Lewis et al., 1984; Kiihn, 1984; Chabre, 1985; Kohl& Hofmann, 1987). Closure of cyclic GMP dependent plasma membrane channels (Matesic & Liebman, 1987) then results inhyperpolarization. Photoac-tivation of rhodopsin is generally consideredto involve the metarhodopsin II (Mil) photointermediate, which is in equilibrium with its precursor metarhodopsin I (MI)(Kiihn, 1984; Chabre, 1985; Kohl & Hofmann, 1987). The MI-MII transition comprises a shift inthe absorption maximum of rhodopsin from 478 to 380 nm, occurs on the millisecond time scale of visual phototransduction, and is known to involve a t Supported by National Institutes of Health GrantEY03754, the
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