CONTROL OF THE REDOX POTENTIAL OF CYTOCHROME-C AND MICROSCOPIC DIELECTRIC EFFECTS IN PROTEINS
CONTROL OF THE REDOX POTENTIAL OF CYTOCHROME-C AND MICROSCOPIC DIELECTRIC EFFECTS IN PROTEINS
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DOI：
10.1021/bi00355a035
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发表时间：
1986-04-08
期刊：
影响因子：
2.9
通讯作者：
WARSHEL, A
中科院分区：
文献类型：
--
作者：
CHURG, AK;WARSHEL, A
X射线结构信息提供了机会，探讨血红素蛋白的微环境和它们的氧化还原电位之间的关系定量。这可以通过将蛋白质视为其氧化还原中心的“溶剂”并计算还原和氧化血红素的静电能之间的差异来完成。这样的计算在这里，应用蛋白质偶极-朗之万偶极（PDLD）模型细胞色素c。计算重点是评估细胞色素c的氧化还原电位与细胞色素c水解形成的八肽-甲硫氨酸复合物之间的差异。相应的差异（. apprx. 7 kcal/mol）通过PDLD计算来解释。发现蛋白质基本上为血红素提供低介电常数，这使氧化血红素不稳定（相对于其在水中的能量）。电荷丙酸对血红素的影响进行了初步研究。结果发现，这些基团的负电荷是在一个亲水性的，而不是一个疏水性的环境，蛋白质-水系统提供了有效的高介电常数为他们与血红素的相互作用。的细胞色素的介电效应的双重性质（低介电常数的血红素的自能和高介电常数的电荷-电荷相互作用）进行了讨论。这项工作的结果与还原和氧化细胞色素c的折叠能之间的差异是一致的。
X-ray structural information provides the opportunity to explore quantitatively the relation between the microenvironments of heme proteins and their redox potentials. This can be done by considering the protein as a "solvent" for its redox center and calculating the difference between the electrostatic energy of the reduced and oxidized heme. Such calculations are presented here, applying the protein dipoles-Langevin dipoles (PDLD) model to cytochrome c. The calculations focus on an evaluation of the difference between the redox potentials to cytochrome c and the octapeptide-methionine complex formed by hydrolysis of cytochrome c. The corresponding difference (.apprx. 7 kcal/mol) is accounted for by the PDLD calculations. It is found that the protein provides basically a low dielectric environement for the heme, which destabilizes the oxidized heme (relative to its energy in water). The effect of the charge propinic acids on the heme is examined in a preliminary way. It is found that the negative charges of these groups are in a hydrophilic rather than a hydrophobic environment and that the protein-water system provides as effective high dielectric constant for their interaction with the heme. The dual nature of the dielectric effect of the cytochrome (a low dielectric constant for the self-energy of the heme and a high dielectric constant for charge-charge interactions) is discussed. The findings of this work are consistent with the difference between the folding energies of the reduced and oxidized cytochrome c.