Effect of Substitution of Proline‐77 to Aspartate on the Light‐Driven Proton Release of Bacteriorhodopsin
Effect of Substitution of Proline‐77 to Aspartate on the Light‐Driven Proton Release of Bacteriorhodopsin
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DOI：
10.1111/j.1751-1097.2012.01146.x
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发表时间：
2012-07
影响因子：
3.3
通讯作者：
Yazhuo Wang;Yingchun Zhao;Ming Ming-Ming;Jia Wu;Weida Huang;Jiandong Ding
中科院分区：
文献类型：
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作者：
Yazhuo Wang;Yingchun Zhao;Ming Ming-Ming;Jia Wu;Weida Huang;Jiandong Ding
野生型细菌视紫红质（BR）和另一种视网膜蛋白质古视紫红质4（AR4）都是光驱动的质子泵，但由于AR4中质子释放复合物（PRC）的pKa较高，因此在中性pH下闪光照射时表现出相反的质子释放和摄取时间顺序。由于BR细胞外侧第77位残基为脯氨酸（P），而AR 4为天冬氨酸（D），因此我们在本研究中将BR中的P77突变为D。发现新的点突变显著影响质子释放动力学和pH依赖性。在闪光激发下，在中性pH下观察到P77D的“快质子释放"、“质子摄取”和“慢质子释放”三个组分。M中间体中PRC的pKa从野生型的5.6增加到7.0，并变得更接近AR 4中的pKa，其为8.4。D85和PRC之间的耦合强度也减弱，正如预期的那样。这些数据表明，AR 4中的第77位残基在很大程度上解释了两种质子泵之间的差异。
Wild‐type bacteriorhodopsin (BR) and another retinal protein archaerhodopsin 4 (AR4) are both light‐driven proton pumps, but exhibit opposite temporal orders of proton release and uptake upon a flash illumination at neutral pH due to a higher pKa of proton release complex (PRC) in AR4. Since the 77th residue in the extracellular side is proline (P) in BR, but aspartic acid (D) in AR4, we have mutated P77 in BR by D in this study. The new point mutation was found to affect the kinetics of proton release and the pH dependence significantly. Upon a flash excitation, three components “fast proton release,”“proton uptake” and “slow proton release” were observed at neutral pH in P77D. The pKa of PRC in the M intermediate was increased from 5.6 in the wild‐type to 7.0, and became closer to that in AR4, which is 8.4. The coupling strength between D85 and PRC were also weakened, as expected. These data indicate that the 77th residue in AR4 greatly account for the difference between the two proton pumps.