Interplay between CN- Ligands and the Secondary Coordination Sphere of the H-Cluster in [FeFe]-Hydrogenases
Interplay between CN- Ligands and the Secondary Coordination Sphere of the H-Cluster in [FeFe]-Hydrogenases
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DOI：
10.1021/jacs.7b08735
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发表时间：
2017-12-20
影响因子：
15
通讯作者：
Winkler, Martin
中科院分区：
文献类型：
--
作者：
Lampret, Oliver;Adamska-Venkatesh, Agnieszka;Winkler, Martin
[FeFe]-氢化（H-簇）的催化辅因子由连接到双核铁-硫簇（2FeH）的一般立方烷[4Fe-4S]-簇（4FeH）组成，所述双核铁-硫簇（2FeH）具有开放配位位点，在所述开放配位位点处发生质子到分子氢的可逆转化。（2FeH）亚位具有由三个CO和两个CN-配体组成的双原子配位球，其影响其氧化还原性质并为FTIR光谱提供优良的探针。CO伸缩振动是非常敏感的氧化还原变化内的H-簇催化循环过程中发生的，而CN-信号似乎是相对惰性的这些影响。这可能是由于CN-配体通过氢键将（2FeH）单元紧密锚定到蛋白质环境的更多结构作用。在这项工作中，我们探讨了影响的CN-配体的FTIR光谱和催化的第二配体球内的结构变化的影响。通过比较野生型酶和两种诱变变体的FTIR光谱，我们能够分配的H-簇的不同氧化还原状态的（2FeH）网站的各个CN-配体的IR信号。此外，蛋白质膜电化学揭示了近端CN-配体的次级配位球的靶向操作（即，最接近（4FeH）位点）可以影响催化偏置。这些发现突出了蛋白质环境的重要性，重新调整的H-簇在个别酶的催化功能，并提供了有价值的信息，人工氢化酶模拟物的设计。
The catalytic cofactor of [FeFe]-hydrogenses (H-cluster) is composed of a generic cubane [4Fe-4S]-cluster (4FeH ) linked to a binuclear iron-sulfur cluster (2FeH) that has an open coordination site at which the reversible conversion of protons to Molecular hydrogen occurs. The (2FeH) subsite features a diatomic coordination sphere composed of three CO and two CN- ligands affecting its redox properties and providing excellent probes for FTIR spectroscopy. The CO stretch vibrations are very sensitive to the redox changes within the H-cluster occurring during the catalytic cycle, whereas the CN- signals seem to be relatively inert to these effects. This could be due to the more structural role of the CN- ligands tightly anchoring the (2FeH) unit to the protein environment through hydrogen bonding. In this work we explore the effects of structural changes within the secondary ligand sphere affecting the CN- ligands on FTIR spectroscopy and catalysis. By comparing the FTIR spectra of wild-type enzyme and two mutagenesis variants, we are able to assign the IR signals of the individual CN- ligands of the (2FeH) site for different redox states of the H-cluster. Moreover, protein film electrochemistry reveals that targeted manipulation of the secondary coordination sphere of the proximal CN- ligand (i.e., closest to the (4FeH) site) can affect the catalytic bias. These findings highlight the importance of the protein environment for re-adjusting the catalytic features of the H-cluster in individual enzymes and provide valuable information for the design of artificial hydrogenase mimics.