Solid-state 2H NMR structure of retinal in metarhodopsin I.
Solid-state 2H NMR structure of retinal in metarhodopsin I.
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DOI：
10.1021/ja058738
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发表时间：
2006-08
影响因子：
15
通讯作者：
G. Salgado;A. Struts;Katsunori Tanaka;S. Krane;K. Nakanishi;Michael F. Brown
中科院分区：
文献类型：
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作者：
G. Salgado;A. Struts;Katsunori Tanaka;S. Krane;K. Nakanishi;Michael F. Brown
由于光的吸收，视紫红质的结构和光化学变化对于理解视觉信号的过程至关重要。我们调查的结构trans-retinal在metarhodopsin I光中间体（MI），其中的retinylidene辅因子作为拮抗剂的功能。视紫红质使用（2）在C5、C9或C13甲基上H-标记并用1-棕榈酰基-2-油酰基-sn-甘油基-3-磷酸胆碱重构的视黄醛再生。通过等电位离心将膜对齐，然后将支持的双层中的视紫红质漂白并在MI状态下冷冻捕获。根据静态单轴分布分析低温脂质凝胶状态下定向视紫红质的固态（2）H NMR光谱（Nevzorov，A.一、Moltke，S.; Heyn，M. P的;布朗，M。F. J. Am. 1999，121，7636-7643）。线形分析使我们能够获得甲基键的取向相对于膜正常的存在下，大量的排列紊乱（马赛克蔓延）。甲基基团的相对取向被用来计算三个不同的平面，代表的多烯链和β-紫罗兰酮环的视黄醛之间的有效扭转角。假设一个三平面模型，一个较小的扭曲结构被发现为视网膜在MI相比，黑暗状态。我们的研究结果与光子能量如何在蛋白质内被引导以允许紧张的视网膜构象放松，从而形成受体的激活状态有关。
The structural and photochemical changes in rhodopsin due to absorption of light are crucial for understanding the process of visual signaling. We investigated the structure of trans-retinal in the metarhodopsin I photointermediate (MI), where the retinylidene cofactor functions as an antagonist. Rhodopsin was regenerated using retinal that was (2)H-labeled at the C5, C9, or C13 methyl groups and was reconstituted with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine. Membranes were aligned by isopotential centrifugation, and rhodopsin in the supported bilayers was then bleached and cryotrapped in the MI state. Solid-state (2)H NMR spectra of oriented rhodopsin in the low-temperature lipid gel state were analyzed in terms of a static uniaxial distribution (Nevzorov, A. A.; Moltke, S.; Heyn, M. P.; Brown, M. F. J. Am. Chem. Soc. 1999, 121, 7636-7643). The line shape analysis allowed us to obtain the methyl bond orientations relative to the membrane normal in the presence of substantial alignment disorder (mosaic spread). Relative orientations of the methyl groups were used to calculate effective torsional angles between the three different planes that represent the polyene chain and the beta-ionone ring of retinal. Assuming a three-plane model, a less distorted structure was found for retinal in MI compared to the dark state. Our results are pertinent to how photonic energy is channeled within the protein to allow the strained retinal conformation to relax, thereby forming the activated state of the receptor.