Mechanism of primary proton transfer in bacteriorhodopsin
Mechanism of primary proton transfer in bacteriorhodopsin
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DOI：
10.1016/j.str.2004.04.016
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发表时间：
2004-07-01
期刊：
影响因子：
5.7
通讯作者：
Fischer, S
中科院分区：
文献类型：
--
作者：
Bondar, AN;Elstner, M;Fischer, S
细菌视紫红质光循环中假定的中间体的最新结构为质子泵送穿过膜的机制提供了有价值的快照。然而，关键步骤仍然存在很大争议，特别是在视网膜反式-->顺式光异构化后立即发生的质子转移。储存能量的逐渐释放本质上是不平衡的：光循环中间体的填充不仅取决于它们的能量，还取决于它们的相互转化率。为了理解为什么光循环遵循生产性（即泵送）而不是非生产性的松弛路径，有必要了解各个步骤的相对能量势垒。为了区分该过程的许多提议场景，我们计算了其所有可能的最小能量路径。这表明，不是一种，而是三种截然不同的途径具有与实验一致的能量势垒。这一结果调和了对该机制持有的相互矛盾的观点，并提出了一种策略，通过该策略该蛋白质使这一重要步骤具有弹性。
Recent structures of putative intermediates in the bacteriorhodopsin photocycle have provided valuable snapshots of the mechanism by which protons are pumped across the membrane. However, key steps remain highly controversial, particularly the proton transfer occurring immediately after retinal trans-->cis photoisomerization. The gradual release of stored energy is inherently nonequilibrium: which photocycle intermediates are populated depends not only on their energy but also on their interconversion rates. To understand why the photocycle follows a productive (i.e., pumping), rather than some unproductive, relaxation pathway, it is necessary to know the relative energy barriers of individual steps. To discriminate between the many proposed scenarios of this process, we computed all its possible minimum-energy paths. This reveals that not one, but three very different pathways have energy barriers consistent with experiment. This result reconciles the conflicting views held on the mechanism and suggests a strategy by which the protein renders this essential step resilient.