Fungal hydrogenosomes contain mitochondrial heat-shock proteins.
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.
van der Giezen
Mark
M
Department of Zoology, The Natural History Museum, London, United Kingdom.
Birdsey
Graeme M
GM
Horner
David S
DS
Lucocq
John
J
Dyal
Patricia L
PL
Benchimol
Marlene
M
Danpure
Christopher J
CJ
Embley
T Martin
TM
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
D018834:Chaperonin 60; D018840:HSP70 Heat-Shock Proteins; D008164:Luminescent Proteins; D049452:Green Fluorescent Proteins; D006859:Hydrogen