Hydrogen-Induced Structural Changes at the Nickel Site of the Regulatory [NiFe] Hydrogenase from Ralstonia eutropha Detected by X-ray Absorption Spectroscopy

详细信息    查看全文

• 作者：Michael Haumann ; Antje Porthun ; Thorsten Buhrke ; Peter Liebisch ; Wolfram Meyer-Klaucke ; Bä ; rbel Friedrich ; and Holger Dau
• 刊名：Biochemistry
• 出版年：2003
• 出版时间：September 23, 2003
• 年：2003
• 卷：42
• 期：37
• 页码：11004 - 11015
• 全文大小：157K
• 年卷期：v.42,no.37(September 23, 2003)
• ISSN：1520-4995

文摘

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 causeremarkable changes in the spectroscopic properties. The Ni-C EPR signal, indicative of Ni(III), is detectableonly in the RH^+H2 state. XANES and EXAFS spectra indicate a coordination of the Ni in the RH^ox andRH^+H2 that pronouncedly differs from the one in standard [NiFe] hydrogenases. Also, the changes inducedby exposure to H₂ are unique. A drastic modification in the XANES spectra and an upshift of the K-edgeenergy from 8339.8 (RH^ox) to 8341.1 eV (RH^+H2) is observed. The EXAFS spectra indicate a change inthe Ni coordination in the RH upon exposure to H₂. One likely interpretation of the data is the detachmentof one sulfur ligand in RH^+H2 and the binding of additional (O,N) or H ligands. The following Ni oxidationstates and coordinations are proposed: five-coordinated Ni^II(O,N)₂S₃ for RH^ox and six-coordinated Ni^(III)(O,N)₃X₁S₂ [X being either an (O,N) or H ligand] for RH^+H2. Implications of the structural features ofthe Ni site of the RH in relation to its function, hydrogen sensing, are discussed.