Electrostatic field around cytochrome c: theory and energy transfer experiment.
Electrostatic field around cytochrome c: theory and energy transfer experiment.
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细胞色素 c 周围的静电场：理论和能量转移实验。
DOI：
10.1073/pnas.87.23.9503
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发表时间：
1990
影响因子：
11.1
通讯作者：
Matthew,JB
中科院分区：
文献类型：
--
作者：
Northrup,SH;Wensel,TG;Meares,CF;Wendoloski,JJ;Matthew,JB
测量了从三种不同电荷状态的电子激发的Tb(III)络合物到马心铁细胞色素c的“快速扩散”极限中的能量传递作为离子强度的函数。通过对Forster积分(包含Poisson-Boltzmann产生的蛋白质静电势)的数值积分计算的理论速率常数与实验数据进行比较，以评价蛋白质/溶剂界面上蛋白质静电场计算的准确性。使用了两种介电形式：简单的库仑/德拜-胡克尔程序和有限差分法[Warwicker，J.&Watson，H.C.(1982)J.Mol.比奥尔。157,671-679]这解释了低介电性蛋白质内部和不规则的蛋白质/溶剂边界。实验结果与实验吻合较好，并成功地重现了反应的离子强度依赖性。分析了理论速率常数对有效施主球大小和能量转移距离判据的敏感性。对沿细胞色素c的两个分子动力学轨道收集的结构进行了静电势和速率常数的计算。结果表明，蛋白质构象的波动对计算的能量转移速率常数有很大的影响。我们得出结论，蛋白质波动和由此产生的瞬时结构可以在生物或催化活性中发挥重要作用，而这些作用从静态结构的检查中并不明显。对于蛋白质静电学的计算，大规模的低频构象涨落，如带电侧链的重新取向，被确定为与考虑介电边界效应的计算方法一样重要。
Energy transfer in the "rapid diffusion" limit from electronically excited terbium(III) chelates in three different charge states to horse heart ferricytochrome c was measured as a function of ionic strength. Theoretical rate constants calculated by numerical integration of the Forster integral (containing the Poisson-Boltzmann-generated protein electrostatic potential) were compared with the experimental data to evaluate the accuracy of protein electrostatic field calculations at the protein/solvent interface. Two dielectric formalisms were used: a simple coulombic/Debye-Hückel procedure and a finite difference method [Warwicker, J. & Watson, H. C. (1982) J. Mol. Biol. 157, 671-679] that accounts for the low-dielectric protein interior and the irregular protein/solvent boundary. Good agreement with experiment was obtained and the ionic-strength dependence of the reaction was successfully reproduced. The sensitivity of theoretical rate constants to the choices of effective donor sphere size and the energy transfer distance criterion was analyzed. Electrostatic potential and rate-constant calculations were carried out on sets of structures collected along two molecular dynamics trajectories of cytochrome c. Protein conformational fluctuations were shown to produce large variations in the calculated energy transfer rate constant. We conclude that protein fluctuations and the resulting transient structures can play significant roles in biological or catalytic activities that are not apparent from examination of a static structure. For calculating protein electrostatics, large-scale low-frequency conformational fluctuations, such as charged side-chain reorientation, are established to be as important as the computational method for incorporating dielectric boundary effects.