Methionaquinone is a Direct Natural Electron Acceptor for the Membrane-bound Hydrogenase in Hydrogenobacter thermophilus Strain TK-6

The hydrogenase reaction in Hydrogenobacter thermophilus strain TK-6, an obligately autotrophic, thermophilic, aerobic hydrogen-oxidizing bacterium, was studied in the membrane fraction, methionaquinone-depleted membrane, and purified membrane-bound hydrogenase. Both b and c type cytochromes were involved in the hydrogen oxidation. Methionaquinone mediated an electron transport between membrane-bound hydrogenase and cytochrome b560. Methionaquinone was reduced directly by purified hydrogenase. From these results, we conclude that methionaquinone is a direct natural electron acceptor for the membrane-bound hydrogenase in the strain.