Regulation of the Proton Pumping Activity of Bacteriorhodopsin - The influence of Membrane Potential and Proton Gradient

膜蛋白细菌视紫红质（bR）是一种光驱动质子泵。质子转移涉及蛋白质内氨基酸的质子化和去质子化反应。辅因子视网膜的异构化引发了这些化学反应。为了理解质子的输运，有必要在原子细节上确定分子内结构和质子化的变化以及它们是如何耦合的。为了达到这种理解，将解决以下主要问题：—bR在不同状态下可滴定基团的质子化概率是多少？-哪些残基参与质子转移并形成质子转移路径？-膜环境、膜电位和质子梯度如何影响质子化概率？-细菌视紫红质、盐视紫红质、感觉视紫红质II和视紫红质的静电差异是什么，这些差异如何决定它们的功能差异？为了解决与质子转移有关的问题，我们将结合静电计算和方法来寻找质子转移路径。这些计算的结果将被Forschergruppe的其他团队用于更精细的量子力学/分子力学组合计算，以更详细地确定质子转移机制。通过比较靠近视网膜的静电电位，分析各种视网膜蛋白的不同性质。

The membrane protein bacteriorhodopsin (bR) is a light-driven proton pump. The proton transfer involves protonation and deprotonation reactions of amino acids within the protein. The isomerization of the cofactor retinal initiates these chemical reactions. To understand the proton transport, it is necessary to determine the intramolecular structural and protonation changes at atomic detail and how they are coupled. To achieve this understanding, the following main questions will be addressed: - What are the protonation probabilities of the titratable groups in the different states of bR? - Which residues participate in proton transfer and form the proton transfer paths? - How do the membrane environment, the membrane potential, and the proton gradient influence the protonation probabilities? - What are the electrostatic differences between bacteriorhodopsin, halorhodopsin, sensory rhodopsin II, and rhodopsin, how do these differences determine their functional differences? To address the questions related to proton transfer, we will combine electrostatic calculations and methods to search for proton transfer paths. The results of these calculations will be used in more elaborate combined quantum mechanical/molecular mechanical calculations by other teams in the Forschergruppe to determine the proton transfer mechanism in more detail. The different properties of the various retinal proteins will be analyzed by comparing the elecrostatic potentials close to the retinal.