NANOSECOND PHOTOLYSIS OF RHODOPSIN - EVIDENCE FOR A NEW, BLUE-SHIFTED INTERMEDIATE
NANOSECOND PHOTOLYSIS OF RHODOPSIN - EVIDENCE FOR A NEW, BLUE-SHIFTED INTERMEDIATE
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DOI：
10.1021/bi00458a019
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发表时间：
1990-02-13
期刊：
影响因子：
2.9
通讯作者：
KLIGER, DS
中科院分区：
文献类型：
--
作者：
HUG, SJ;LEWIS, JW;KLIGER, DS
通过接近生理温度的纳秒激光光解研究天然牛视紫红质 (RHO) 的早期光解中间体。在用各种能量的477-、532-和560-nm激光脉冲激发以及在5、12、17、21和32°下用477-nm激光激发后收集吸收差光谱。 C. 使用奇异值分解 (SVD) 和全局指数拟合例程对数据进行分析。在通常与红视紫红质到光视紫红质的衰变相关的时间内，观察到与不同光谱变化相关的两个速率常数。考虑了与这一观察结果一致的各种模型。顺序模型显示，在红视紫红质中间体和新中间体 (BSI) 之间存在可逆步骤（BSI 相对于光视紫红质发生蓝移），该模型最适合数据。观察到的和计算出的速率常数的温度依赖性导致线性阿累尼乌斯图。温度依赖性的外推表明，在低于 -100°C 的温度下，视紫红质光解后不应观察到 BSI。 C.讨论了关于人工视色素顺式5,6-二氢异视紫红质和13-去甲基视紫红质的结果。有人提出，BATHO 到 BSI 转变的速率受到紧密蛋白质环境中紧张的全反式视网膜发色团松弛的限制。向 LUMI 的转变涉及发色团松弛与蛋白质松弛同时发生。虽然第一个过程受到发色团变化的强烈影响，但第二个转变似乎更多地由蛋白质松弛决定。
Early photolysis intermediates of native bovine rhodopsin (RHO) are investigated by nanosecond laser photolysis near physiological temperature. Absorption difference spectra are collected after excitation with 477-, 532-, and 560-nm laser pulses of various energies and with 477-nm laser excitation at 5, 12, 17, 21, and 32.degree. C. The data are analyzed by using singular-value decomposition (SVD) and a global exponential fitting routine. Two rate constants associated with distinct spectral changes are observed during the time normally associated with the decay of bathorhodopsin to lumirhodopsin. Various models consistent with this observation are considered. A sequential model in which there is a reversible step between a bathorhodopsin intermediate and a new intermediate (BSI), which is blue-shifted relative to lumirhodopsin, is shown to best fit the data. The temperature dependence of the observed and calculated rate constants leads to linear Arrhenius plots. Extrapolation of the temperature dependence suggests that BSI should not be observable after rhodopsin photolysis at temperatures below -100.degree. C. The results are discussed with regard to the artificial visual pigments cis-5,6-dihydroisorhodopsin and 13-demethylrhodopsin. It is proposed that the rate of the BATHO to BSI transition is limited by the relaxation of the strained all-trans-retinal chromophore within a tight protein environment. The transition to LUMI involves chromophore relaxation concurrent with protein relaxation. While the first process is strongly affected by changes in the chromophore, the second transition seems to be determined more by protein relaxation.