Modeling gating charge and voltage changes in response to charge separation in membrane proteins.
Modeling gating charge and voltage changes in response to charge separation in membrane proteins.
复制标题
模拟响应膜蛋白电荷分离的门控电荷和电压变化。
DOI：
10.1073/pnas.1411573111
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发表时间：
2014
影响因子：
11.1
通讯作者：
Warshel,Arieh
中科院分区：
文献类型：
--
作者：
Kim,Ilsoo;Chakrabarty,Suman;Brzezinski,Peter;Warshel,Arieh
测量膜蛋白内电荷分离引起的电压变化可以提供有关电荷传输和位移过程机制的基本信息。最近的一个例子是细胞色素氧化酶的研究。然而，根据电荷当量数和传输距离来解释观察到的电压变化绝非微不足道或独特的。使用连续方法来描述电压生成可能会涉及很大的不确定性，并且尚无法进行可靠的微观模拟。在这里，我们尝试通过使用膜蛋白的粗粒度模型来解决这个问题，其中包括对膜、电解质和电极的明确描述。该模型评估蛋白质内电荷转移时的门控电荷和电极电位（比较测量电压）。通过将与细菌光合反应中心的电子和质子转移相关的测量电压变化与使用我们的粗粒度模型计算的电压变化进行比较来评估模型的准确性。计算再现了实验观察结果，因此表明该方法具有普遍用途。有趣的是，我们发现不同空间方向（但垂直于膜的距离相同）的电荷分离过程可以给出相似的观察到的电压变化，这表明在使用电荷位移与电压变化之间关系的简化解释时应谨慎。
Measurements of voltage changes in response to charge separation within membrane proteins can offer fundamental information on mechanisms of charge transport and displacement processes. A recent example is provided by studies of cytochromecoxidase. However, the interpretation of the observed voltage changes in terms of the number of charge equivalents and transfer distances is far from being trivial or unique. Using continuum approaches to describe the voltage generation may involve significant uncertainties and reliable microscopic simulations are not yet available. Here, we attempt to solve this problem by using a coarse-grained model of membrane proteins, which includes an explicit description of the membrane, the electrolytes, and the electrodes. The model evaluates the gating charges and the electrode potentials (c.f. measured voltage) upon charge transfer within the protein. The accuracy of the model is evaluated by a comparison of measured voltage changes associated with electron and proton transfer in bacterial photosynthetic reaction centers to those calculated using our coarse-grained model. The calculations reproduce the experimental observations and thus indicate that the method is of general use. Interestingly, it is found that charge-separation processes with different spatial directions (but the same distance perpendicular to the membrane) can give similar observed voltage changes, which indicates that caution should be exercised when using simplified interpretation of the relationship between charge displacement and voltage changes.