用于分析质子化状态以及追踪质子转移途径的工具,并以球形红细菌光合反应中心为例进行说明。
Tools for analyzing protonation states and for tracing proton transfer pathways with examples from the Rb. sphaeroides photosynthetic reaction centers.
作者信息
Wei Rongmei Judy, Khaniya Umesh, Mao Junjun, Liu Jinchan, Batista Victor S, Gunner M R
机构信息
Ph.D. Program in Chemistry, The Graduate Center, City University of New York, New York, NY, 10016, USA.
Department of Physics, City College of New York, New York, NY, 10031, USA.
出版信息
Photosynth Res. 2023 Apr;156(1):101-112. doi: 10.1007/s11120-022-00973-0. Epub 2022 Oct 29.
Protons participate in many reactions. In proteins, protons need paths to move in and out of buried active sites. The vectorial movement of protons coupled to electron transfer reactions establishes the transmembrane electrochemical gradient used for many reactions, including ATP synthesis. Protons move through hydrogen bonded chains of waters and hydroxy side chains via the Grotthuss mechanism and by proton binding and release from acidic and basic residues. MCCE analysis shows that proteins exist in a large number of protonation states. Knowledge of the equilibrium ensemble can provide a rational basis for setting protonation states in simulations that fix them, such as molecular dynamics (MD). The proton path into the Q site in the bacterial reaction centers (RCs) of Rb. sphaeroides is analyzed by MD to provide an example of the benefits of using protonation states found by the MCCE program. A tangled web of side chains and waters link the cytoplasm to Q. MCCE analysis of snapshots from multiple trajectories shows that changing the input protonation state of a residue in MD biases the trajectory shifting the proton affinity of that residue. However, the proton affinity of some residues is more sensitive to the input structure. The proton transfer networks derived from different trajectories are quite robust. There are some changes in connectivity that are largely restricted to the specific residues whose protonation state is changed. Trajectories with Q are compared with earlier results obtained with Q [Wei et. al Photosynthesis Research volume 152, pages153-165 (2022)] showing only modest changes. While introducing new methods the study highlights the difficulty of establishing the connections between protein conformation.
质子参与许多反应。在蛋白质中,质子需要进出埋藏的活性位点的路径。与电子转移反应耦合的质子矢量运动建立了用于许多反应(包括ATP合成)的跨膜电化学梯度。质子通过水和羟基侧链的氢键链,通过Grotthuss机制以及通过质子与酸性和碱性残基的结合与释放来移动。MCCE分析表明,蛋白质以大量质子化状态存在。平衡系综的知识可以为在诸如分子动力学(MD)等固定质子化状态的模拟中设置质子化状态提供合理依据。通过MD分析了球形红细菌细菌反应中心(RCs)中进入Q位点的质子路径,以提供使用MCCE程序发现的质子化状态的益处的示例。一系列纠结的侧链和水将细胞质与Q连接起来。对来自多个轨迹的快照进行MCCE分析表明,在MD中改变残基的输入质子化状态会使轨迹发生偏差,从而改变该残基的质子亲和力。然而,一些残基的质子亲和力对输入结构更敏感。从不同轨迹导出的质子转移网络相当稳健。连接性的一些变化在很大程度上仅限于质子化状态发生变化的特定残基。将有Q的轨迹与早期使用Q获得的结果进行比较[Wei等人,光合作用研究第152卷,第153 - 165页(2022年)],结果显示变化不大。虽然引入了新方法,但该研究突出了建立蛋白质构象之间联系的困难。