THE INVOLVEMENT OF WATER AT THE RETINAL BINDING SITE IN RHODOPSIN AND EARLY LIGHT‐INDUCED INTRAMOLECULAR PROTON TRANSFER
THE INVOLVEMENT OF WATER AT THE RETINAL BINDING SITE IN RHODOPSIN AND EARLY LIGHT‐INDUCED INTRAMOLECULAR PROTON TRANSFER
复制标题
视网膜结合位点水参与视紫红质和早期光诱导分子内质子转移
DOI：
10.1111/j.1751-1097.1981.tb05329.x
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发表时间：
1981
影响因子：
3.3
通讯作者：
H. Shichi
中科院分区：
文献类型：
--
作者：
C. Rafferty;H. Shichi
摘要牛视杆外节膜的空气干燥膜的广泛脱水诱导视紫红质吸收光谱的完全可逆变化，表明样品中超过50%的视紫红质分子中的亚视黄基席夫碱的去质子化。这表明水参与了视紫红质中席夫碱质子化的位点。相比之下，变视紫红质I的光谱对类似的脱水条件具有抗性，这意味着在变视紫红质I中质子化的机制方面存在显著差异。对脱水膜的光化学性质进行了探讨。去质子化视紫红质的光激发（λmax 390 nm）引起发色团的大的红移。在室温下的主要光产物是光谱相似的metarhodopsin I（λmax，478 nm）。这些发现表明，涉及席夫碱质子的分子内质子转移可能发生在视觉周期的早期阶段，在形成后视紫红质I之前或期间。
Abstract Extensive dehydration of air‐dried films of bovine rod outer segment membranes induces fully reversible changes in the absorption spectrum of rhodopsin, indicative of deprotonation of the retinylidene Schiff base in more than 50% of the rhodopsin molecules in the sample. This suggests that water is involved at the site of the Schiff base protonation in rhodopsin. In contrast, the spectrum of metarhodopsin I is resistant to similar dehydrating conditions, implying a significant difference in the mechanism for protonation in metarhodopsin I. The photochemistry of dehydrated membranes was also explored. Photoexcitation of deprotonated rhodopsin (λmax 390 nm) induces a large bathochromic shift of the chromophore. The major photoproduct at room temperature was spectrally similar to metarhodopsin I (λmax, 478 nm). These findings suggest that intramolecular proton transfer involving the Schiff base proton may occur in the earlier stages of the visual cycle, prior to or during the formation of metarhodopsin I.