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Issue 12, 2010
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The iron-site structure of [Fe]-hydrogenase and model systems: an X-ray absorption near edge spectroscopy study

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Abstract

The [Fe]-hydrogenase is an ideal system for studying the electronic properties of the low spin iron site that is common to the catalytic centres of all hydrogenases. Because they have no auxiliary iron-sulfur clusters and possess a cofactor containing a single iron centre, the [Fe]-hydrogenases are well suited for spectroscopic analysis of those factors required for the activation of molecular hydrogen. Specifically, in this study we shed light on the electronic and molecular structure of the iron centre by XAS analysis of [Fe]-hydrogenase from Methanocaldococcus jannashii and five model complexes (Fe(ethanedithiolate)(CO)2(PMe3)2, [K(18-crown-6)]2[Fe(CN)2(CO)3], K[Fe(CN)(CO)4], K3[Fe(III)(CN)6], K4[Fe(II)(CN)6]). The different electron donors have a strong influence on the iron absorption K-edge energy position, which is frequently used to determine the metal oxidation state. Our results demonstrate that the K-edges of Fe(II) complexes, achieved with low-spin ferrous thiolates, are consistent with a ferrous centre in the [Fe]-hydrogenase from Methanocaldococcus jannashii. The metal geometry also strongly influences the XANES and thus the electronic structure. Using in silico simulation, we were able to reproduce the main features of the XANES spectra and describe the effects of individual donor contributions on the spectra. Thereby, we reveal the essential role of an unusual carbon donor coming from an acyl group of the cofactor in the determination of the electronic structure required for the activity of the enzyme.

Graphical abstract: The iron-site structure of [Fe]-hydrogenase and model systems: an X-ray absorption near edge spectroscopy study

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Publication details

The article was received on 28 Oct 2009, accepted on 08 Jan 2010 and first published on 28 Jan 2010


Article type: Paper
DOI: 10.1039/B922557A
Citation: Dalton Trans., 2010,39, 3057-3064
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    The iron-site structure of [Fe]-hydrogenase and model systems: an X-ray absorption near edge spectroscopy study

    M. Salomone-Stagni, F. Stellato, C. M. Whaley, S. Vogt, S. Morante, S. Shima, T. B. Rauchfuss and W. Meyer-Klaucke, Dalton Trans., 2010, 39, 3057
    DOI: 10.1039/B922557A

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