These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


PUBMED FOR HANDHELDS

Search MEDLINE/PubMed


  • Title: Hydrogen-induced structural changes at the nickel site of the regulatory [NiFe] hydrogenase from Ralstonia eutropha detected by X-ray absorption spectroscopy.
    Author: Haumann M, Porthun A, Buhrke T, Liebisch P, Meyer-Klaucke W, Friedrich B, Dau H.
    Journal: Biochemistry; 2003 Sep 23; 42(37):11004-15. PubMed ID: 12974636.
    Abstract:
    For the first time, the nickel site of the hydrogen sensor of Ralstonia eutropha, the regulatory [NiFe] hydrogenase (RH), was investigated by X-ray absorption spectroscopy (XAS) at the nickel K-edge. The oxidation state and the atomic structure of the Ni site were investigated in the RH in the absence (air-oxidized, RH(ox)) and presence of hydrogen (RH(+H2)). Incubation with hydrogen is found to cause remarkable changes in the spectroscopic properties. The Ni-C EPR signal, indicative of Ni(III), is detectable only in the RH(+H2) state. XANES and EXAFS spectra indicate a coordination of the Ni in the RH(ox) and RH(+H2) that pronouncedly differs from the one in standard [NiFe] hydrogenases. Also, the changes induced by exposure to H(2) are unique. A drastic modification in the XANES spectra and an upshift of the K-edge energy from 8339.8 (RH(ox)) to 8341.1 eV (RH(+H2)) is observed. The EXAFS spectra indicate a change in the Ni coordination in the RH upon exposure to H(2). One likely interpretation of the data is the detachment of one sulfur ligand in RH(+H2) and the binding of additional (O,N) or H ligands. The following Ni oxidation states and coordinations are proposed: five-coordinated Ni(II)(O,N)(2)S(3) for RH(ox) and six-coordinated Ni((III))(O,N)(3)X(1)S(2) [X being either an (O,N) or H ligand] for RH(+H2). Implications of the structural features of the Ni site of the RH in relation to its function, hydrogen sensing, are discussed.
    [Abstract] [Full Text] [Related] [New Search]