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Resonance Raman Spectroscopic Analysis of the [NiFe] Active Site and the Proximal [4Fe-3S] Cluster of an O-2-Tolerant Membrane-Bound Hydrogenase in the Crystalline State
Citation key Siebert2015
Author Siebert, Elisabeth and Rippers, Yvonne and Frielingsdorf, Stefan and Fritsch, Johannes and Schmidt, Andrea and Kalms, Jacqueline and Katz, Sagie and Lenz, Oliver and Scheerer, Patrick and Paasche, Lars and Pelmenschikov, Vladimir and Kuhlmann, Uwe and Mroginski, Maria Andrea and Zebger, Ingo and Hildebrandt, Peter
Pages 13785–13796
Year 2015
DOI 10.1021/acs.jpcb.5b04119
Journal Journal of Physical Chemistry B
Volume 119
Number 43
Abstract We have applied resonance Raman (RR) spectroscopy on single protein crystals of the O-2-tolerant membrane-bound [NiFe] hydrogenase (MBH from Ralstonia eutropha) which catalyzes the splitting of H-2 into protons and electrons. RR spectra taken from 65 MBH samples in different redox states were analyzed in terms of the respective component spectra of the active site and the unprecedented proximal [4Fe-3S] cluster using a combination of statistical methods and global fitting procedures. These component spectra of the individual cofactors were compared with calculated spectra obtained by quantum mechanics/molecular mechanics (QM/MM) methods. Thus, the recently discovered hydroxyl-coordination of one iron in the [4Fe-3S] cluster was confirmed. Infrared (IR) microscopy of oxidized MBH crystals revealed the [NiFe] active site to be in the Ni-r-B [Ni(III)] and Ni-r-S [Ni(II)] states, whereas RR measurements of these crystals uncovered the Ni-a-S [Ni(II)] state as the main spectral component, suggesting its in situ formation via photodissociation of the assumed bridging hydroxyl or water ligand. On the basis of QM/MM calculations, individual band frequencies could be correlated with structural parameters for the Ni-a-S state as well as for the Ni-L state, which is formed upon photodissociation of the bridging hydride of H-2-reduced active site states.
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