Cyanide Binding to [FeFe]-Hydrogenase Stabilizes the Alternative Configuration of the Proton Transfer Pathway |
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| Authors: | Dr Jifu Duan Dr Anja Hemschemeier David J Burr Dr Sven T Stripp Prof Eckhard Hofmann Prof Thomas Happe |
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| Institution: | 1. Department of Plant Biochemistry, Faculty of Biology and Biotechnology, Photobiotechnology, Ruhr University Bochum, Universitätsstrasse 150, 44801 Bochum, Germany;2. Department of Physics, Experimental Biophysics and Space Sciences, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany;3. Department of Biophysics, Experimental Molecular Biophysics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany;4. Department of Biophysics, Faculty of Biology and Biotechnology, Protein Crystallography, Ruhr University Bochum, Universitätsstrasse 150, 44801 Bochum, Germany |
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| Abstract: | Hydrogenases are H2 converting enzymes that harbor catalytic cofactors in which iron (Fe) ions are coordinated by biologically unusual carbon monoxide (CO) and cyanide (CN−) ligands. Extrinsic CO and CN−, however, inhibit hydrogenases. The mechanism by which CN− binds to FeFe]-hydrogenases is not known. Here, we obtained crystal structures of the CN−-treated FeFe]-hydrogenase CpI from Clostridium pasteurianum. The high resolution of 1.39 Å allowed us to distinguish intrinsic CN− and CO ligands and to show that extrinsic CN− binds to the open coordination site of the cofactor where CO is known to bind. In contrast to other inhibitors, CN− treated crystals show conformational changes of conserved residues within the proton transfer pathway which could allow a direct proton transfer between E279 and S319. This configuration has been proposed to be vital for efficient proton transfer, but has never been observed structurally. |
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| Keywords: | Cyanide Hydrogen Bonds Hydrogenase Proton Transfer Pathway X-Ray Diffraction |
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