Unique Spectroscopic Properties of the H-Cluster in a Putative Sensory [FeFe] Hydrogenase
Unique Spectroscopic Properties of the H-Cluster in a Putative Sensory [FeFe] Hydrogenase
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DOI：
10.1021/jacs.7b11287
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发表时间：
2018-01-24
影响因子：
15
通讯作者：
Ogata, Hideaki
中科院分区：
文献类型：
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作者：
Chongdar, Nipa;Birrell, James A.;Ogata, Hideaki
预测感觉型[FeFe]氢化酶通过检测细胞环境的H-2水平在转录调节中发挥作用。这些氢化酶含有在活性位点口袋中具有不同修饰的氢化酶结构域，随后是Per-Arnt-Sim（PAS）结构域。到目前为止，这些酶的生理功能、生化或光谱特性都还没有被研究。在这里，我们提出了一个人工成熟的，推定的感官[FeFe]氢化酶从海栖热袍菌（HydS）的表征。该酶表现出较低的氢转化活性比原型[FeFe]氢化酶和减少抑制CO。使用FTIR光谱电化学和EPR光谱，三个氧化还原态的活性位点进行了鉴定。最氧化态的光谱特征非常类似于那些从原型[FeFe]氢化酶的H-ox状态，而单和双还原态的FTIR光谱显示出很大的差异。两个还原态的FTIR谱带相对于H-ox态强烈红移，表明在二铁位点处还原，但保留了桥连CO配体。HydS的独特的功能和光谱特征进行了讨论方面的可能作用改变的氨基酸残基影响的H-簇的电子性质。
Sensory type [FeFe] hydrogenases are predicted to play a role in transcriptional regulation by detecting the H-2 level of the cellular environment. These hydrogenases contain the hydrogenase domain with distinct modifications in the active site pocket, followed by a Per-Arnt-Sim (PAS) domain. As yet, neither the physiological function nor the biochemical or spectroscopic properties of these enzymes have been explored. Here, we present the characterization of an artificially maturated, putative sensory [FeFe] hydrogenase from Thermotoga maritima (HydS). This enzyme shows lower hydrogen conversion activity than prototypical [FeFe] hydrogenases and a reduced inhibition by CO. Using FTIR spectroelectrochemistry and EPR spectroscopy, three redox states of the active site were identified. The spectroscopic signatures of the most oxidized state closely resemble those of the H-ox state from the prototypical [FeFe] hydrogenases, while the FTIR spectra of both singly and doubly reduced states show large differences. The FTIR bands of both the reduced states are strongly red-shifted relative to the H-ox state, indicating reduction at the diiron site, but with retention of the bridging CO ligand. The unique functional and spectroscopic features of HydS are discussed with regard to the possible role of altered amino acid residues influencing the electronic properties of the H-cluster.