Complete Charge Regulation by a Redox Enzyme Upon Single Electron Transfer
Complete Charge Regulation by a Redox Enzyme Upon Single Electron Transfer
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氧化还原酶在单电子转移时完成电荷调节
DOI：
10.1002/anie.202001452
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
Shaw, Bryan F.
中科院分区：
文献类型：
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作者：
Zhang, Ao Yun;Koone, Jordan C.;Dashnaw, Chad M.;Zahler, Collin T.;Shaw, Bryan F.
金属蛋白部分调节电子转移（ET）时净电荷(Z)的程度最近首次使用蓝蛋白、细胞色素c和肌红蛋白的“蛋白质电荷阶梯”进行了测量。化学。Int。Ed.2018 57 (19), 5364 - 5368; Angew。Chem.2018, 130, 5462 - 5466]。在这里，我们发现Cu， Zn超氧化物歧化酶（SOD1）在蛋白质中是独一无二的，它能够抵抗单个ET的净电荷变化(例如，ΔZET（SOD1)=0.05±0.08每个电子，而ΔZET(Cyt‐c)=1.19±0.02）。SOD1对净电荷的总调节归因于铜还原时桥接组氨酸的质子化，产生在铜氧化状态下等电的氧化还原中心。SOD1的电荷调节将防止对铜ET上残留pKa的长距离库仑扰动，允许SOD1的“静电环”在扩散限制还原和超氧化物氧化过程中以相同的亲和力（在铜的两种氧化还原状态下）吸引超氧化物。
The degree by which metalloproteins partially regulate net charge (Z) upon electron transfer (ET) was recently measured for the first time using “protein charge ladders” of azurin, cytochrome c, and myoglobin [Angew. Chem. Int. Ed.2018,57(19), 5364–5368;Angew. Chem.2018,130, 5462–5466]. Here, we show that Cu, Zn superoxide dismutase (SOD1) is unique among proteins in its ability to resist changes in net charge upon single ET (e.g., ΔZET(SOD1)=0.05±0.08 per electron, compared to ΔZET(Cyt‐c)=1.19±0.02). This total regulation of net charge by SOD1 is attributed to the protonation of the bridging histidine upon copper reduction, yielding redox centers that are isoelectric at both copper oxidation states. Charge regulation by SOD1 would prevent long range coulombic perturbations to residue pKa’s upon ET at copper, allowing SOD1’s “electrostatic loop” to attract superoxide with equal affinity (at both redox states of copper) during diffusion‐limited reduction and oxidation of superoxide.