Biochemical studies on membrane-bound [NiDe] hydrogenases related to complex I

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Project summary In the recent years a group of multisubunit membrane bound [NiFe] hydrogenases with significant sequence similarity to complex I of the mitochondrial and bacterial respiratory chain has been identified. The list of enzymes includes Escherichia coli hydrogenases-3 and -4, CO-induced hydrogenase from Rhodospirillum rubrum and Ech hydrogenase from Methanosarcina barkeri. These enzymes are characterized by five conserved subunits which have homologs in complex I of the respiratory chain of bacteria and mitochondria. In complex I these subunits are assumed to be essential for proton-pumping. The close relationship of these hydrogenases to complex I indicates that these enzymes and complex I have a common evolutionary ancestor. A proton-pumping function has been postulated for these hydrogenases but not yet proven. Thus far no detailed biochemical studies with one of these hydrogenases, isolated as intact protein complex, have been performed. The objectives of the biochemical studies, which will be performed with Ech in this project, are the elucidation of functional similarities between complex I and these hydrogenases.