Characterization of the photochemical reaction cycle of proteorhodopsin.
Characterization of the photochemical reaction cycle of proteorhodopsin.
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DOI：
10.1016/s0006-3495(03)74934-0
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发表时间：
2003-02
影响因子：
3.4
通讯作者：
G. Varo;L. Brown;M. Lakatos;J. Lanyi
中科院分区：
文献类型：
--
作者：
G. Varo;L. Brown;M. Lakatos;J. Lanyi
分析了最近被描述的视网膜蛋白蛋白视紫红质在光周期中的吸收变化。在pH 9.5的瞬变光谱中，它作为一个光驱动的质子泵，揭示了三个光谱上不同的中间体K，M和N的存在，类似于细菌视紫红质的光中间体。基于四个波长的含时吸收动力学信号的模型分析表明，还存在两个光谱上无声的中间体，并导致在衰减到初始态PR之前，由五个中间体K，M1，M2，N和PR‘组成的顺序反应方案。没有观察到类似L的中间体，可能是出于动力学原因。通过测量取向样品的光生电信号，可以确定每种中间体的生电活性。前三个中间体(K、M1和M2)的生电活性有较小的负值，但后三个组分对应于N和PR‘中间体和PR为正值，且大两个数量级。这些状态对跨膜的质子转移做出了主要贡献。根据吸收动力学信号的温度依赖关系，计算了光循环的能量方案。
Absorption changes in the photocycle of the recently described retinal protein, proteorhodopsin, are analyzed. The transient spectra at pH 9.5, where it acts as a light-driven proton pump, reveal the existence of three spectrally different intermediates, K, M, and N, named in analogy with the photointermediates of bacteriorhodopsin. Model analysis based on time-dependent absorption kinetic signals at four wavelengths suggested the existence of two more spectrally silent intermediates and lead to a sequential reaction scheme with five intermediates, K, M1, M2, N, and PR′, before decay to the initial state PR. An L-like intermediate was not observed, probably for kinetic reasons. By measuring the light-generated electric signal of an oriented sample, the electrogenicity of each intermediate could be determined. The electrogenicities of the first three intermediates (K, M1, and M2) have small negative value, but the last three components, corresponding to the N and PR′ intermediates and PR, are positive and two-orders-of-magnitude larger. These states give the major contributions to the proton translocation across the membrane. The energetic scheme of the photocycle was calculated from the temperature-dependence of the absorption kinetic signals.