Effects of ligation and folding on reduction potentials of heme proteins
Effects of ligation and folding on reduction potentials of heme proteins
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DOI：
10.1021/ja982536e
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发表时间：
1998-12-30
影响因子：
15
通讯作者：
Gray, HB
中科院分区：
文献类型：
--
作者：
Tezcan, FA;Winkler, JR;Gray, HB
铁细胞色素c(Fe(II)cytc)类似于10kcal/mol(410 MeV)，比Fe(III)cytc在去折叠过程中更稳定，这主要是由于疏水包裹和增强铁-蛋氨酸键稳定了亚铁血红素。为了确定这两个组分的大小，我们测量了N-乙酰蛋氨酸(AcMet)和咪唑与细胞色素c的含铁和亚铁的N-乙酰微过氧化物酶-8(AcMP8)的结合常数。我们的结果表明，还原后血红素的AcMet亲和力显著增加，电化学测量证实，这一增加解释了Fe(II)和Fe(III)Cytc之间410-MeV稳定性差异的130 meV。折叠蛋白质的还原电位上移240 mV主要归因于环境中的水。基于对八种结构表征的c型细胞色素的电势的分析。我们的分析表明，通过改变辅因子暴露在溶剂中，血红素蛋白的电位可以调节大约500 mV。
Ferrocytochrome c (Fe(II)cyt c) is similar to 10 kcal/mol (410 meV) more stable toward unfolding than Fe(III)cyt c, owing mainly to the stabilization of the ferroheme by hydrophobic encapsulation and enhanced iron-methionine bonding. To determine the magnitudes of these two components, we have measured the binding constants of N-acetylmethionine (AcMet) and imidazole to ferric and ferrous N-acetylmicroperoxidase-8 (AcMP8), a heme-containing proteolytic fragment of cyt c. Our results show that the AcMet affinity of the heme significantly increases upon reduction, as confirmed by electrochemical measurements, and this increase accounts for 130 meV of the 410-meV stability difference between Fe(II)- and Fe(III)cyt c. A 240-mV upshift in reduction potential in the folded protein is attributed mainly to water exclusion from the heme environment, based on an analysis of the potentials of eight structurally characterized c-type cytochromes. Our analysis shows that the potentials of heme proteins can be tuned by roughly 500 mV through variations in cofactor exposure to solvent.