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Spectroscopic Insights into the Oxygen-tolerant Membrane-associated [NiFe] Hydrogenase of eutropha H16
Citation key ISI:000266730900024
Author Saggu, Miguel and Zebger, Ingo and Ludwig, Marcus and Lenz, Oliver and Friedrich, Baerbel and Hildebrandt, Peter and Lendzian, Friedhelm
Pages 16264-16276
Year 2009
ISSN 0021-9258
DOI 10.1074/jbc.M805690200
Address 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3996 USA
Journal J. Biol. Chem.
Volume 284
Number 24
Month JUN 12
Publisher AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
Abstract This study provides the first spectroscopic characterization of the membrane-bound oxygen-tolerant [NiFe] hydrogenase (MBH) from Ralstonia eutropha H16 in its natural environment, the cytoplasmic membrane. The H-2-converting MBH is composed of a large subunit, harboring the [NiFe] active site, and a small subunit, capable in coordinating one [3Fe4S] and two [4Fe4S] clusters. The hydrogenase dimer is electronically connected to a membrane-integral cytochrome b. EPR and Fourier transform infrared spectroscopy revealed a strong similarity of the MBH active site with known [NiFe] centers from strictly anaerobic hydrogenases. Most redox states characteristic for anaerobic [NiFe] hydrogenases were identified except for one remarkable difference. The formation of the oxygen-inhibited Ni-u-A state was never observed. Furthermore, EPR data showed the presence of an additional paramagnetic center at high redox potential (+ 290 mV), which couples magnetically to the [3Fe4S] center and indicates a structural and/or redox modification at or near the proximal [4Fe4S] cluster. Additionally, significant differences regarding the magnetic coupling between the Ni-a-C state and [4Fe4S] clusters were observed in the reduced form of the MBH. The spectroscopic properties are discussed with regard to the unusual oxygen tolerance of this hydrogenase and in comparison with those of the solubilized, dimeric form of the MBH.
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