Interaction-induced redox switch in the electron transfer complex rusticyanin-cytochrome c4
Interaction-induced redox switch in the electron transfer complex rusticyanin-cytochrome c4
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DOI：
10.1074/jbc.274.43.30365
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发表时间：
1999-10-22
影响因子：
4.8
通讯作者：
Nitschke, W
中科院分区：
文献类型：
--
作者：
Giudici-Orticoni, MT;Guerlesquin, F;Nitschke, W
蓝铜蛋白rusticyanin从嗜酸性蛋白细菌氧化亚铁硫杆菌分离显示pH依赖性的氧化还原中点电位与pK值为7的氧化形式的蛋白质。在pK值以上观察到的光学光谱和EPR光谱的改变的性质表明，在组氨酸配体的ε-氮上发生氧化还原连接的去质子化作用。黄花菜青苷与其可能的电子传递伙伴细胞色素c（4）之间形成复合物，诱导黄花菜青苷的氧化还原中点电位降低超过100 mV，同时光谱变化与游离形式的pK值以上观察到的变化相似。因此，复合物的形成基本上改变了表面暴露的组氨酸配体对铜离子的pK值，从而调节了铜位点的氧化还原中点电位。与其他蓝铜蛋白的报告的比较表明，表面暴露的组氨酸配体被用作氧化还原调节装置，这组可溶性电子载体的许多成员。
The blue copper protein rusticyanin isolated from the acidophilic proteobacterium Thiobacillus ferrooxidans displays a pH-dependent redox midpoint potential with a pK value of 7 on the oxidized form of the protein. The nature of the alterations of optical and EPR spectra observed above the pK value indicated that the redox-linked deprotonation occurs on the epsilon-nitrogen of the histidine ligands to the copper ion. Complex formation between rusticyanin and its probable electron transfer partner, cytochrome c(4), induced a decrease of rusticyanin's redox midpoint potential by more than 100 mV together with spectral changes similar to those observed above the pK value of the free form. Complex formation thus substantially modifies the pK value of the surface-exposed histidine ligand to the copper ion and thereby tunes the redox midpoint potential of the copper site. Comparisons with reports on other blue copper proteins suggest that the surface-exposed histidine ligand is employed as a redox tuning device by many members of this group of soluble electron carriers.