Energy-converting [NiFe] hydrogenases from archaea and extremophiles: ancestors of complex I.
[NiFe] hydrogenases are well-characterized enzymes that have a key function in the H2 metabolism of various microorganisms. In the recent years a subfamily of [NiFe] hydrogenases with unique properties has been identified. The members of this family form multisubunit membrane-bound enzyme complexes composed of at least four hydrophilic and two integral membrane proteins. These six conserved subunits, which built the core of these hydrogenases, have closely related counterparts in energy-conserving NADH:quinone oxidoreductases (complex I). However, the reaction catalyzed by these hydrogenases differs significantly from the reaction catalyzed by complex I. For some of these hydrogenases the physiological role is to catalyze the reduction of H+ with electrons derived from reduced ferredoxins or poly-ferredoxins. This exergonic reaction is coupled to energy conservation by means of electron-transport phosphorylation. Other members of this hydrogenase family mainly function to provide the cell with reduced ferredoxin with H2 as electron donor in a reaction driven by reverse electron transport. As complex I these hydrogenases function as ion pumps and have therefore been designated as energy-converting [NiFe] hydrogenases.
Hedderich
Reiner
R
Max-Planck-Institut für terrestrische Mikrobiologie, Karl-von-Frisch-Strasse, D-35043 Marburg, Germany. hedderic@staff.uni-marburg.de
D001105:Archaea / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology*; D017124:Conserved Sequence; D042967:Electron Transport Complex I / Q000737:chemistry* / Q000378:metabolism*; D004735:Energy Transfer / Q000502:physiology*; D019143:Evolution, Molecular; D016931:Halobacteriales / Q000502:physiology; D006864:Hydrogenase / Q000737:chemistry* / Q000378:metabolism*; D010084:Oxidation-Reduction; D017386:Sequence Homology, Amino Acid
C043296:nickel-iron hydrogenase; D006864:Hydrogenase; D042967:Electron Transport Complex I