title: Hydrogenosomal succinyl-CoA synthetase from the rumen-dwelling fungus Neocallimastix patriciarum; an energy-producing enzyme of mitochondrial origin.
abstract: Hydrogenosomes are hydrogen-producing organelles that are related to mitochondria and found in a variety of evolutionarily unrelated anaerobic microbial eukaryotes. Similar to classic mitochondria, hydrogenosomes contain the enzyme catalyzing the only reaction of the citric acid cycle directly producing energy; succinyl-CoA synthetase. We have isolated and characterized the genes encoding both subunits of this enzyme from the anaerobic chytrid fungus Neocallimastix patriciarum, a model organism in hydrogenosome research. Both subunits contain all characteristic features of this enzyme, including predicted hydrogenosomal targeting signals. Phylogenetic analyses of succinyl-CoA synthetase clearly indicate its mitochondrial ancestry, both by affiliation with mitochondrially localized fungal homologues and by the sisterhood of the eukaryotic succinyl-CoA synthetase clade with alpha-proteobacteria. Our analyses of the Trichomonas vaginalis SCS sequences also confirmed the mitochondrial affiliation of these hydrogenosomal enzymes, in contrast to previous results. While both hydrogenosomal and mitochondrial succinyl-CoA synthetase homologues have been identified, no succinyl-CoA synthetase proteins were identifiable in taxa possessing another mitochondrially derived organelle, the mitosome. Our analyses further confirm the mitochondrial ancestry of the Neocallimastix hydrogenosome and sheds light upon the stepwise process by which mitochondria evolve into alternate forms of the organelle.
authors.affiliation: Department of Zoology, the Natural History Museum, Cromwell Road, London SW7 5BD, UK.
authors.forename: Joel B
authors.initials: JB
authors.lastname: Dacks
authors.forename: Patricia L
authors.initials: PL
authors.lastname: Dyal
authors.forename: T Martin
authors.initials: TM
authors.lastname: Embley
authors.forename: Mark
authors.initials: M
authors.lastname: van der Giezen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D008928:Mitochondria / Q000201:enzymology*; D008954:Models, Biological; D008969:Molecular Sequence Data; D020088:Neocallimastix / Q000201:enzymology* / Q000235:genetics; D015388:Organelles / Q000201:enzymology*; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D013389:Succinate-CoA Ligases / Q000235:genetics*
chemical_list: D013389:Succinate-CoA Ligases