Two tyrosyl radicals stabilize high oxidation states in cytochrome C oxidase for efficient energy conservation and proton translocation.
Two tyrosyl radicals stabilize high oxidation states in cytochrome C oxidase for efficient energy conservation and proton translocation.
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DOI：
10.1021/ja210535w
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发表时间：
2012-03-14
影响因子：
15
通讯作者：
Gerfen, Gary J.
中科院分区：
文献类型：
--
作者：
Yu, Michelle A.;Egawa, Tsuyoshi;Shinzawa-Itoh, Kyoko;Yoshikawa, Shinya;Guallar, Victor;Yeh, Syun-Ru;Rousseau, Denis L.;Gerfen, Gary J.
用电子顺磁共振（EPR）研究了氧化型牛细胞色素c氧化酶（bCcO）与过氧化氢（H2 O2）的反应，以确定自由基中间体的性质。两个不同的自由基的宽度为12和46 G的直接观察到的X-带EPR在bCcO与H2 O2在pH 6和pH 8的反应。高频EPR（D-带）提供了基于良好分辨的g-张量的两个自由基的酪氨酸分配。宽自由基（46 G）表现出类似于通过UV照射在L-酪氨酸上产生的自由基和在许多其他酶系统中鉴定的酪氨酰基自由基的g值。相比之下，窄基团（12 G）的g值偏离L-Tyr的趋势类似于酪氨酸上的基团，在邻位取代。X-带EPR表明两个酪氨酰自由基的β-亚甲基质子的取向不同。12 G宽的自由基具有最小的超精细结构，并且可以使用bCcO中后修饰的Y244所特有的参数来拟合。46 G宽基团具有广泛的超精细结构，可以用与Y129一致的参数拟合。结果得到了混合量子力学和分子力学计算的支持。除了提供光谱证据的自由基上形成的post-acetonally改性的酪氨酸在CCO，这项研究解决了备受争议的争论是否广泛的自由基在低pH值的牛酶是酪氨酸或色氨酸。自由基的形成和迁移质子易位的可能作用进行了讨论。
The reaction of oxidized bovine cytochrome c oxidase (bCcO) with hydrogen peroxide (H2O2) was studied by electron paramagnetic resonance (EPR) to determine the properties of radical intermediates. Two distinct radicals with widths of 12 and 46 G are directly observed by X-band EPR in the reaction of bCcO with H2O2 at pH 6 and pH 8. High-frequency EPR (D-band) provides assignments to tyrosine for both radicals based on well-resolved g-tensors. The wide radical (46 G) exhibits g-values similar to a radical generated on L-Tyr by UV-irradiation and to tyrosyl radicals identified in many other enzyme systems. In contrast, the g-values of the narrow radical (12 G) deviate from L-Tyr in a trend akin to the radicals on tyrosines with substitutions at the ortho position. X-band EPR demonstrates that the two tyrosyl radicals differ in the orientation of their β-methylene protons. The 12 G wide radical has minimal hyperfine structure and can be fit using parameters unique to the post-translationally modified Y244 in bCcO. The 46 G wide radical has extensive hyperfine structure and can be fit with parameters consistent with Y129. The results are supported by mixed quantum mechanics and molecular mechanics calculations. In addition to providing spectroscopic evidence of a radical formed on the post-translationally modified tyrosine in CcO, this study resolves the much debated controversy of whether the wide radical seen at low pH in the bovine enzyme is a tyrosine or tryptophan. The possible role of radical formation and migration in proton translocation is discussed.
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影响因子：
4.8
作者：
Chen, YR;Gunther, MR;Mason, RP
通讯作者：
Mason, RP
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Einarsdóttir, O
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作者：
Duboc-Toia, C;Hassan, AK;Heider, J
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