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Reduction of unusual iron-sulfur clusters in the H-2-sensing regulatory Ni-Fe hydrogenase from Ralstonia eutropha H16
Zitatschlüssel ISI:000229113700010
Autor Buhrke, T and Loscher, S and Lenz, O and Schlodder, E and Zebger, I and Andersen, L K and Hildebrandt, P and Meyer-Klaucke, W and Dau, H and Friedrich, B and Haumann, M
Seiten 19488-19495
Jahr 2005
ISSN 0021-9258
DOI 10.1074/jbc.M500601200
Adresse 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3996 USA
Journal J. Biol. Chem.
Jahrgang 280
Nummer 20
Monat MAY 20
Verlag AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
Zusammenfassung The regulatory Ni-Fe hydrogenase (RH) from Ralstonia eutropha functions as a hydrogen sensor. The RH consists of the large subunit HoxC housing the Ni-Fe active site and the small subunit HoxB containing Fe-S clusters. The heterolytic cleavage of H-2 at the Ni-Fe active site leads to the EPR-detectable Ni-C state of the protein. For the first time, the simultaneous but EPR-invisible reduction of Fe-S clusters during Ni-C state formation was demonstrated by changes in the UV-visible absorption spectrum as well as by shifts of the iron K-edge from x-ray absorption spectroscopy in the wildtype double dimeric RHWT [HoxBC](2) and in a monodimeric derivative designated RHstop lacking the C-terminal 55 amino acids of HoxB. According to the analysis of iron EXAFS spectra, the Fe-S clusters of HoxB pronouncedly differ from the three Fe-S clusters in the small subunits of crystallized standard Ni-Fe hydrogenases. Each HoxBC unit of RHWT seems to harbor two [2Fe-2S] clusters in addition to a 4Fe species, which may be a [4Fe-3S-3O] cluster. The additional 4Fe-cluster was absent in RHstop. Reduction of Fe-S clusters in the hydrogen sensor RH may be a first step in the signal transduction chain, which involves complex formation between [HoxBC](2) and tetrameric HoxJ protein, leading to the expression of the energy converting Ni-Fe hydrogenases in R. eutropha.
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