An Escherichia coli hydrogenase-3-type hydrogenase in methanogenic archaea

Methanogenic archaea are known to contain two types of [NiFe] hydrogenases designated F420-reducing hydrogenase and F420-non-reducing hydrogenase. We report here that they additionally contain Escherichia coli hydrogenase-3-type [NiFe] hydrogenases. The evidence is based on biochemical studies and analysis of the subunit primary structure of this hydrogenase (designated Ech) purified from membranes of acetate-grown cells of Methanosarcina barkeri. The subunits EchE and EchC of the EchABCDEF complex showed 34% and 45% sequence identity to the nickel-containing large subunit HycE and to the iron-sulfur cluster containing small subunit HycG, respectively, of the hydrogenase in the formate hydrogen lyase complex from E. coli. Analysis of the totally sequenced genomes of Methanococcus jannaschii and Methanobacterium thermoautotrophicum strain deltaH revealed that these organisms contain similar open reading frames, indicating the presence of an E. coli hydrogenase-3-type hydrogenase also in these methanogenic archaea.