Selzer T, Schreiber G
Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel.
J Mol Biol. 1999 Mar 26;287(2):409-19. doi: 10.1006/jmbi.1999.2615.
The rate of association of proteins is dictated by diffusion, but can be enhanced by favorable electrostatic forces. Here the relationship between the electrostatic energy of interaction, and the kinetics of protein-complex formation was analyzed for the protein pairs of: hirudin-thrombin, acetylcholinesterase-fasciculin and barnase-barstar, and for a panel of point mutants of these proteins. Electrostatic energies of interaction were calculated as the difference between the electrostatic energy of the complex and the sum of the energies of the two individual proteins, using the computer simulation package DelPhi. Calculated electrostatic energies of interaction were compared to experimentally determined rates of association. One kcal/mol of Coulombic interaction energy increased the rate of association by a factor of 2.8, independent of the protein-complex or mutant analyzed. Electrostatic energies of interaction were also determined from the salt dependence of the association rate constant, using the same basic equation as for the theoretical calculation. A Brönsted analysis of the electrostatic energies of interactions plotted versus experimentally determined ln(rate)s of association shows a linear relation between the two, with a beta value close to 1. This is interpreted as the energy of the transition state varies according to the electrostatic interaction energy, fitting a two state model for the association reaction. Calculating electrostatic rate enhancement from the electrostatic interaction energy can be used as a powerful tool to design protein complexes with altered rates of association and affinities.
蛋白质的结合速率由扩散决定，但有利的静电力可增强结合速率。本文分析了水蛭素 - 凝血酶、乙酰胆碱酯酶 - 束丝菌素和芽孢杆菌RNA酶 - 芽孢杆菌RNA酶抑制剂这几对蛋白质及其一系列点突变体的相互作用静电能与蛋白质复合物形成动力学之间的关系。利用计算机模拟软件DelPhi，将复合物的静电能与两个单独蛋白质的能量之和的差值计算为相互作用的静电能。将计算得到的相互作用静电能与实验测定的结合速率进行比较。每1千卡/摩尔的库仑相互作用能可使结合速率提高2.8倍，这与所分析的蛋白质复合物或突变体无关。还使用与理论计算相同的基本方程，根据结合速率常数的盐依赖性来确定相互作用的静电能。对绘制的相互作用静电能与实验测定的结合速率的ln(速率)值进行布朗斯特分析，结果表明两者之间呈线性关系，β值接近1。这被解释为过渡态的能量根据静电相互作用能而变化，符合结合反应的双态模型。根据静电相互作用能计算静电速率增强可作为设计具有改变的结合速率和亲和力的蛋白质复合物的有力工具。
