title: Fungal hydrogenosomes contain mitochondrial heat-shock proteins.
abstract: At least three groups of anaerobic eukaryotes lack mitochondria and instead contain hydrogenosomes, peculiar organelles that make energy and excrete hydrogen. Published data indicate that ciliate and trichomonad hydrogenosomes share common ancestry with mitochondria, but the evolutionary origins of fungal hydrogenosomes have been controversial. We have now isolated full-length genes for heat shock proteins 60 and 70 from the anaerobic fungus Neocallimastix patriciarum, which phylogenetic analyses reveal share common ancestry with mitochondrial orthologues. In aerobic organisms these proteins function in mitochondrial import and protein folding. Homologous antibodies demonstrated the localization of both proteins to fungal hydrogenosomes. Moreover, both sequences contain amino-terminal extensions that in heterologous targeting experiments were shown to be necessary and sufficient to locate both proteins and green fluorescent protein to the mitochondria of mammalian cells. This finding, that fungal hydrogenosomes use mitochondrial targeting signals to import two proteins of mitochondrial ancestry that play key roles in aerobic mitochondria, provides further strong evidence that the fungal organelle is also of mitochondrial ancestry. The extraordinary capacity of eukaryotes to repeatedly evolve hydrogen-producing organelles apparently reflects a general ability to modify the biochemistry of the mitochondrial compartment.
authors.affiliation: Department of Zoology, The Natural History Museum, London, United Kingdom.
authors.forename: Mark
authors.initials: M
authors.lastname: van der Giezen
authors.forename: Graeme M
authors.initials: GM
authors.lastname: Birdsey
authors.forename: David S
authors.initials: DS
authors.lastname: Horner
authors.forename: John
authors.initials: J
authors.lastname: Lucocq
authors.forename: Patricia L
authors.initials: PL
authors.lastname: Dyal
authors.forename: Marlene
authors.initials: M
authors.lastname: Benchimol
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Danpure
authors.forename: T Martin
authors.initials: TM
authors.lastname: Embley
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018834:Chaperonin 60 / Q000235:genetics*; D049452:Green Fluorescent Proteins; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics*; D006859:Hydrogen / Q000378:metabolism*; D008164:Luminescent Proteins / Q000378:metabolism; D008928:Mitochondria / Q000235:genetics*; D008969:Molecular Sequence Data; D020088:Neocallimastix / Q000235:genetics*; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid
chemical_list: D018834:Chaperonin 60; D018840:HSP70 Heat-Shock Proteins; D008164:Luminescent Proteins; D049452:Green Fluorescent Proteins; D006859:Hydrogen