Weber P C, Tollin G
J Biol Chem. 1985 May 10;260(9):5568-73.
The interaction of three different c-type cytochromes with flavodoxin has been studied by computer graphics modelling and computational methods. Flavodoxin and each cytochrome can make similar hypothetical electron transfer complexes that are characterized by nearly coplanar arrangement of the prosthetic groups, close intermolecular contacts at the protein-protein interface, and complementary intermolecular salt linkages. Computation of the electrostatic free energy of each complex showed that all were electrostatically stable. However, both the magnitude and behavior of the electrostatic stabilization as a function of solution ionic strength differed for the three cytochrome c-flavodoxin complexes. Variation in the computed electrostatic stabilization appears to reflect differences in the surface distribution of all charged groups in the complex, rather than differences localized at the site of intermolecular contact. The computed electrostatic association constants for the complexes and the measured kinetic rates of electron transfer in solution show a remarkable similarity in their ionic strength dependence. This correlation suggests electrostatic interactions influence electron transfer rates between protein molecules at the intermolecular association step. Comparative calculations for the three cytochrome c-flavodoxin complexes show that these ionic strength effects also involve all charged groups in both redox partners.
通过计算机图形建模和计算方法研究了三种不同的c型细胞色素与黄素氧还蛋白的相互作用。黄素氧还蛋白和每种细胞色素都能形成类似的假设性电子转移复合物，其特征是辅基几乎共面排列、蛋白质-蛋白质界面处分子间紧密接触以及互补的分子间盐键。对每个复合物的静电自由能计算表明，所有复合物在静电方面都是稳定的。然而，三种细胞色素c-黄素氧还蛋白复合物的静电稳定程度及其随溶液离子强度的变化行为有所不同。计算得到的静电稳定变化似乎反映了复合物中所有带电基团表面分布的差异，而不是分子间接触位点处的局部差异。复合物的计算静电缔合常数和溶液中测量的电子转移动力学速率在离子强度依赖性方面表现出显著的相似性。这种相关性表明，静电相互作用在分子间缔合步骤影响蛋白质分子之间的电子转移速率。对三种细胞色素c-黄素氧还蛋白复合物的比较计算表明，这些离子强度效应也涉及两个氧化还原伴侣中的所有带电基团。
