Langen R, Jensen G M, Jacob U, Stephens P J, Warshel A
Department of Chemistry, University of Southern California, Los Angeles 90089-0482.
J Biol Chem. 1992 Dec 25;267(36):25625-7.
The relationship between the three-dimensional structures of iron-sulfur proteins and the redox potentials of their iron-sulfur clusters is of fundamental importance. We report calculations of the redox potentials of the [Fe4S4(S-cys)4]-2/-3 couple in four crystallographically characterized proteins: Azotobacter vinelandii ferredoxin I, Peptococcus aerogenes ferredoxin, Bacillus thermoproteolyticus ferredoxin, and Chromatium vinosum high potential iron protein (HiPIP). Our calculations use the "protein dipoles Langevin dipoles" microscopic electrostatic model, which includes both protein and solvent water. The variations in calculated redox potentials are in excellent agreement with experimental data. In particular, our results confirm the important role of amide groups close to the cluster in separating the potential of C. vinosum HiPIP from those of the other three proteins. However, the potentials of these latter exhibit a substantial range despite extremely similar amide group environments of their clusters. Our results show that the potentials in these proteins are tuned in part by varying the access of solvent water to the neighborhood of the cluster. Our calculations provide the first successful quantitative modeling of the protein control of iron-sulfur cluster redox potentials.
铁硫蛋白的三维结构与其铁硫簇的氧化还原电位之间的关系至关重要。我们报告了对四种晶体结构已明确的蛋白质中[Fe4S4(S-cys)4]-2/-3电对氧化还原电位的计算，这四种蛋白质分别是：棕色固氮菌铁氧化还原蛋白I、产气消化球菌铁氧化还原蛋白、嗜热栖热芽孢杆菌铁氧化还原蛋白以及嗜硫小红卵菌高电位铁蛋白（HiPIP）。我们的计算使用了“蛋白质偶极子 - 朗之万偶极子”微观静电模型，该模型同时考虑了蛋白质和溶剂水。计算得到的氧化还原电位变化与实验数据高度吻合。特别是，我们的结果证实了靠近簇的酰胺基团在将嗜硫小红卵菌HiPIP的电位与其他三种蛋白质的电位区分开来方面所起的重要作用。然而，尽管它们的簇周围酰胺基团环境极为相似，但后三种蛋白质的电位仍呈现出较大范围。我们的结果表明，这些蛋白质中的电位部分是通过改变溶剂水进入簇附近的程度来调节的。我们的计算首次成功地对铁硫簇氧化还原电位的蛋白质控制进行了定量建模。
