title: Phenotypic evidence that the function of the [Fe]-hydrogenase Hmd in Methanococcus maripaludis requires seven hcg (hmd co-occurring genes) but not hmdII.
abstract: The H2 -dependent methylene-tetrahydromethanopterin dehydrogenase (Hmd), also known as the [Fe]-hydrogenase, is found only in methanogens without cytochromes. In contrast to the binuclear metal centers of the [NiFe]- and [FeFe]-hydrogenases, the [Fe]-hydrogenase contains only a single Fe atom, which is coordinated by a novel guanylylpyridinol cofactor in the active site. The biosynthesis of the cofactor is not well understood and the responsible genes are unknown. However, seven genes (hmd co-occurring genes, hcg) encoding proteins of unknown function are always associated with the hmd gene. In the model methanogen Methanococcus maripaludis, we used a genetic background in which a deletion of hmd had a distinct growth phenotype, and made null-mutations in each hcg gene as well as in a gene encoding the Hmd paralog HmdII, which is hypothesized to function as a scaffold for cofactor synthesis. Deletions in all seven hcg genes resulted in the same growth phenotype as a deletion in hmd, suggesting they are required for Hmd function. In all cases, genetic complementation of the mutation restored the wild-type phenotype. A deletion in hmdII had no effect.
authors.affiliation: Department of Microbiology, University of Washington, Seattle, WA, USA.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Lie
authors.forename: Kyle C
authors.initials: KC
authors.lastname: Costa
authors.forename: Daniel
authors.initials: D
authors.lastname: Pak
authors.forename: Varun
authors.initials: V
authors.lastname: Sakesan
authors.forename: John A
authors.initials: JA
authors.lastname: Leigh
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D023061:Gene Order; D006864:Hydrogenase / Q000235:genetics* / Q000378:metabolism*; D007506:Iron-Sulfur Proteins / Q000235:genetics* / Q000378:metabolism*; D017017:Methanococcus / Q000235:genetics* / Q000378:metabolism*; D005810:Multigene Family; D009154:Mutation; D010641:Phenotype
chemical_list: D001426:Bacterial Proteins; D007506:Iron-Sulfur Proteins; C118830:iron hydrogenase; D006864:Hydrogenase