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首页> 外文期刊>Biochemistry >The K79G Mutation Reshapes the Heme Crevice and Alters Redox Properties of Cytochrome c
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The K79G Mutation Reshapes the Heme Crevice and Alters Redox Properties of Cytochrome c

机译：K79G突变重塑血红素缝隙，并改变细胞色素C的氧化还原性质

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The two roles of cytochrome c (cyt c), in oxidative phosphorylation and apoptosis, critically depend on redox properties of its heme iron center. The K79G mutant has served as a parent protein for a series of mutants of yeast iso-1 cyt c. The mutation preserves the Met80 coordination to the heme iron, as found in WT* (K72A/C102S), and many spectroscopic properties of K79G and WT* are indistinguishable. The K79G mutation does not alter the global stability, fold, rate of Met80 dissociation, or thermodynamics of the alkaline transition (pK(a)) of the protein. However, the reduction potential of the heme iron decreases; further, the pK(H) of the trigger group and the rate of the Met-to-Lys ligand exchange associated with the alkaline transition decrease, suggesting changes in the environment of the heme. The rates of electron self-exchange and bimolecular electron transfer (ET) with positively charged inorganic complexes increase, as does the intrinsic peroxidase activity. Analysis of the reaction rates suggests that there is increased accessibility of the heme edge in K79G and supports the importance of the Lys79 site for bimolecular ET reactions of cyt c, including those with some of its native redox partners. Structural modeling rationalizes the observed effects to arise from changes in the volume of the heme pocket and solvent accessibility of the heme group. Kinetic and structural analyses of WT* characterize the properties of the heme crevice of this commonly employed reference variant. This study highlights the important role of Lys79 for defining functional redox properties of cyt c.
机译：细胞色素C（Cyt C），氧化磷酸化和凋亡的两个作用尺寸依赖于其血红素铁中心的氧化还原性能。 K79G突变体已经用作酵母ISO-1 Cyt C的一系列突变体的母体蛋白。突变将MET80与血红素铁的协调保持，如在WT *（K72A / C102s）中所发现的，并且K79G和WT *的许多光谱性质是难以区分的。 K79G突变不会改变全局稳定性，折叠，MET80解离的速率，或碱性转变的热力学（PK（A））。然而，血红素铁的降低潜力降低;此外，触发基团的PK（H）和与碱性转变相关的Met-to-Lys配体交换的速率下降，表明血红素环境的变化。电子自交换和双分子电子转移（ET）具有带正电荷的无机复合物的速率增加，因此本征过氧化物酶活性如此。对反应速率的分析表明，K79G中血红素边缘的可达性增加，支持Lys79位点对Cyt C的BimolecularET反应的重要性，包括其中一些天然氧化还原合作伙伴。结构建模合理化观察到的效果，从血红素组的血红素口袋的体积和溶剂可用性的变化产生。 WT *的动力学和结构分析表征该常用参考变体的血红素缝隙的性质。该研究突出了Lys79用于定义Cyt C的功能氧化还原性能的重要作用。

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