NiFe hydrogenase electron transport

Fig. 1. Proposed electron transport pathway in D. gigas NiFe-hydrogenase. Selected distances are given in angstroms. Modified with permission from Ref. (157).

Leger C, Jones AK, Albracht SPJ, Armstrong FAA. 2002. Effect of a dispersion of interfacial electron transfer rates on steady state catalytic electron transport in [NiFe]-hydrogenase and other enzymes. J Phys Chem B 106 13058-13063. 

Pershad, H. R., Duff, J. L., Heering, H. A., Duin, E. C., Albracht, S. P. and Armstrong, F. A. (1999) Catalytic electron transport in Chromatium vinosum [NiFe]-hydrogenase Application of voltammetry in detecting redox-active centers and establishing that hydrogen oxidation is very fast even at potentials close to the reversible H+/H2 value. Biochemistry, 38, 8992-9. 

Pereira et al. (1998) provided biochemical evidence that electron transfer from either iron-only or NiFe-hydrogenases to HmcA is possible, although at a slow rate. The increase in electron-transfer rate by addition of cytochrome C3 indicates that a more probable electron-transport path is from hydrogen through hydrogenase and cytochrome C3 to HmcA. 

Figure 18.4. Proposed biocorrosion model for cathodic electron depolarization of mild steel by D. vulgaris Hildenborough. CM, cytoplasmic membrane HMC, high molecular weight cytochrome [Fe] Fl2ase, iron hydrogenase [NiFe] H2ase, nickel iron hydrogenase ETS, electron transport system.

Electron-transferring subunit, nickel-containing hydrogenases, 38 409-410 Electron transport blue copper proteins, 36 378 NiFe hydrogenase, 47 16-17 Electron volt, 16 73... 

The [2Fe 2S], [3Fe S], and [4Fe S] clusters that are found in simple Fe S proteins are also constituents of respiratory and photosynthetic electron transport chains. Multicluster Fe S enzymes such as hydrogenase, formate dehydrogenase, NADH dehydrogenase, and succinate dehydrogenase feed electrons into respiratory chains, while others such as nitrate reductase, fhmarate reductase, DMSO reductase, and HDR catalyze the terminal step in anaerobic electron transport chains that utihze nitrate, fumarate, DMSO, and the CoB S S CoM heterodisulfide as the respiratory oxidant. All comprise membrane anchor polypeptide(s) and soluble subunits on the membrane surface that mediate electron transfer to or from Mo cofactor (Moco), NiFe, Fe-S cluster or flavin active sites. Multiple Fe-S clusters define electron transport pathways between the active site and the electron donor or... 

The small subunit contains three [FeS] clusters that are involved in the electron transport to/from the active [NiFe] center (Fig. 1). In the catalytically active hydrogenases, a [4Fe4S] proximal cluster is located near the [NiFe] center,... 

Figure 1. Schematic view of an [NiFe] hydrogenase and the active site. Shown are the 2 subunits with the active site (NiFe center), the proton channel, and the hydrogen access channel in the targe subunit and the electron transport chain (3 FeS centers) in the small subunit. The structure of the catalytic site is shown on the right, which is based on the x-ray crystallographic analysis of D. vulgaris Miyazaki F [6]. Note that Fe is six-coordinate, while Ni is only five-coordinate the free coordination site at Ni is marked by an arrow. For further details see text.

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