title: Presence of a member of the mitochondrial carrier family in hydrogenosomes: conservation of membrane-targeting pathways between hydrogenosomes and mitochondria.
abstract: A number of microaerophilic eukaryotes lack mitochondria but possess another organelle involved in energy metabolism, the hydrogenosome. Limited phylogenetic analyses of nuclear genes support a common origin for these two organelles. We have identified a protein of the mitochondrial carrier family in the hydrogenosome of Trichomonas vaginalis and have shown that this protein, Hmp31, is phylogenetically related to the mitochondrial ADP-ATP carrier (AAC). We demonstrate that the hydrogenosomal AAC can be targeted to the inner membrane of mitochondria isolated from Saccharomyces cerevisiae through the Tim9-Tim10 import pathway used for the assembly of mitochondrial carrier proteins. Conversely, yeast mitochondrial AAC can be targeted into the membranes of hydrogenosomes. The hydrogenosomal AAC contains a cleavable, N-terminal presequence; however, this sequence is not necessary for targeting the protein to the organelle. These data indicate that the membrane-targeting signal(s) for hydrogenosomal AAC is internal, similar to that found for mitochondrial carrier proteins. Our findings indicate that the membrane carriers and membrane protein-targeting machinery of hydrogenosomes and mitochondria have a common evolutionary origin. Together, they provide strong evidence that a single endosymbiont evolved into a progenitor organelle in early eukaryotic cells that ultimately give rise to these two distinct organelles and support the hydrogen hypothesis for the origin of the eukaryotic cell.
authors.affiliation: Department of Microbiology and Immunology, University of California, Los Angeles, California 90095, USA.
authors.forename: S D
authors.initials: SD
authors.lastname: Dyall
authors.forename: C M
authors.initials: CM
authors.lastname: Koehler
authors.forename: M G
authors.initials: MG
authors.lastname: Delgadillo-Correa
authors.forename: P J
authors.initials: PJ
authors.lastname: Bradley
authors.forename: E
authors.initials: E
authors.lastname: Plümper
authors.forename: D
authors.initials: D
authors.lastname: Leuenberger
authors.forename: C W
authors.initials: CW
authors.lastname: Turck
authors.forename: P J
authors.initials: PJ
authors.lastname: Johnson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D004734:Energy Metabolism; D019143:Evolution, Molecular; D005656:Fungal Proteins / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D000226:Mitochondrial ADP, ATP Translocases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D021382:Protein Sorting Signals / Q000737:chemistry / Q000378:metabolism; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D014246:Trichomonas vaginalis / Q000737:chemistry* / Q000166:cytology
chemical_list: D002352:Carrier Proteins; D005656:Fungal Proteins; C405950:Hmp31 protein, Trichomonas vaginalis; D008565:Membrane Proteins; C112225:PET9 protein, S cerevisiae; D021382:Protein Sorting Signals; D015800:Protozoan Proteins; D029701:Saccharomyces cerevisiae Proteins; D000226:Mitochondrial ADP, ATP Translocases