title: Ancestral and derived protein import pathways in the mitochondrion of Reclinomonas americana.
abstract: The evolution of mitochondria from ancestral bacteria required that new protein transport machinery be established. Recent controversy over the evolution of these new molecular machines hinges on the degree to which ancestral bacterial transporters contributed during the establishment of the new protein import pathway. Reclinomonas americana is a unicellular eukaryote with the most gene-rich mitochondrial genome known, and the large collection of membrane proteins encoded on the mitochondrial genome of R. americana includes a bacterial-type SecY protein transporter. Analysis of expressed sequence tags shows R. americana also has components of a mitochondrial protein translocase or "translocase in the inner mitochondrial membrane complex." Along with several other membrane proteins encoded on the mitochondrial genome Cox11, an assembly factor for cytochrome c oxidase retains sequence features suggesting that it is assembled by the SecY complex in R. americana. Despite this, protein import studies show that the RaCox11 protein is suited for import into mitochondria and functional complementation if the gene is transferred into the nucleus of yeast. Reclinomonas americana provides direct evidence that bacterial protein transport pathways were retained, alongside the evolving mitochondrial protein import machinery, shedding new light on the process of mitochondrial evolution.
authors.affiliation: Department of Biochemistry & Molecular Biology, Monash University, Clayton, Australia.
authors.forename: Janette
authors.initials: J
authors.lastname: Tong
authors.forename: Pavel
authors.initials: P
authors.lastname: Dolezal
authors.forename: Joel
authors.initials: J
authors.lastname: Selkrig
authors.forename: Simon
authors.initials: S
authors.lastname: Crawford
authors.forename: Alastair G B
authors.initials: AG
authors.lastname: Simpson
authors.forename: Nicholas
authors.initials: N
authors.lastname: Noinaj
authors.forename: Susan K
authors.initials: SK
authors.lastname: Buchanan
authors.forename: Kipros
authors.initials: K
authors.lastname: Gabriel
authors.forename: Trevor
authors.initials: T
authors.lastname: Lithgow
mesh_terms: D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D002467:Cell Nucleus / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism; D056890:Eukaryota / Q000235:genetics* / Q000648:ultrastructure; D019143:Evolution, Molecular; D022761:Gene Transfer, Horizontal; D057927:Hydrophobic and Hydrophilic Interactions; D008928:Mitochondria / Q000648:ultrastructure; D033681:Mitochondrial Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D008957:Models, Genetic; D008969:Molecular Sequence Data; D021382:Protein Sorting Signals / Q000235:genetics; D021381:Protein Transport / Q000235:genetics*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D033681:Mitochondrial Membrane Transport Proteins; D021382:Protein Sorting Signals; D011994:Recombinant Proteins; D051546:Cyclooxygenase 2