Identification of a Catalytic Iron-Hydride at the H-Cluster of [FeFe]-Hydrogenase
Identification of a Catalytic Iron-Hydride at the H-Cluster of [FeFe]-Hydrogenase
复制标题
DOI：
10.1021/jacs.6b11409
复制
发表时间：
2017-01-11
影响因子：
15
通讯作者：
King, Paul W.
中科院分区：
文献类型：
--
作者：
Mulder, David W.;Guo, Yisong;King, Paul W.
氢化酶将电化学电位耦合到氢-2和质子的可逆化学转化中，但反应机理和中间体的组成尚不完全清楚。在这篇通讯中，我们描述了莱茵衣藻（Chlamydomonas reinhardtii） [FeFe]-氢化酶的氢化物结合态（H-hyd）的生物物理性质。[FeFe]-加氢酶的催化H簇由[4Fe-4S]亚簇（[4Fe-4S](H)）组成，该亚簇由半胱氨酸硫醇与偶氮二硫酸桥接的2Fe亚簇（[2Fe](H)）与CO和CN-配体连接。穆斯堡尔分析和密度泛函理论（DFT）计算表明，H-hyd由还原的[4Fe-4S](H)（+）与末端结合的二铁[2Fe](H)组成。[2Fe](H)亚簇远端Fe的穆斯堡尔同分异构体位移异常低，证明了H-hyd中Fe-氢化物的存在。氢氢化物的DFT模型表明，铁氢化物是氢键网络的一部分，与附近的桥接氮二硫酸酯促进快速质子交换和催化翻转。
Hydrogenases couple electrochemical potential to the reversible chemical transformation of H-2 and protons, yet the reaction mechanism and composition of intermediates are not fully understood. In this Communication we describe the biophysical properties of a hydride-bound state (H-hyd) of the [FeFe]-hydrogenase from Chlamydomonas reinhardtii. The catalytic H-cluster of [FeFe]-hydrogenase consists of a [4Fe-4S] subcluster ([4Fe-4S](H)) linked by a cysteine thiol to an azadithiolate-bridged 2Fe subcluster ([2Fe](H)) with CO and CN- ligands. Mossbauer analysis and density functional theory (DFT) calculations show that H-hyd consists of a reduced [4Fe-4S](H)(+) coupled to a diferrous [2Fe](H) with a terminally bound Fe-hydride. The existence of the Fe-hydride in H-hyd was demonstrated by an unusually low Mossbauer isomer shift of the distal Fe of the [2Fe](H) subcluster. A DFT model of H-hyd shows that the Fe-hydride is part of a H bonding network with the nearby bridging azadithiolate to facilitate fast proton exchange and catalytic turnover.