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Hydrogenase; Iron–guanylylpyridinol-cofactor; Methanogenic archaea; Iron complex; X-ray crystal structure; X-ray absorption spectroscopy
Abstract:
[Fe]-hydrogenase is one of three types of enzymes known to activate H2. Crystal structure analysis recently revealed that its active site iron is ligated square-pyramidally by Cys176-sulfur, two CO, an ‘‘unknown” ligand and the sp2-hybridized nitrogen of a unique iron–guanylylpyridinol-cofactor. We report here on the structure of the C176A mutated enzyme crystallized in the presence of dithiothreitol (DTT). It suggests an iron center octahedrally coordinated by one DTT-sulfur and one DTToxygen, two CO, the 2-pyridinol’s nitrogen and the 2-pyridinol’s 6-formylmethyl group in an acyliron ligation. This result led to a re-interpretation of the iron ligation in the wild-type
