title: Origin and Evolutionary Alteration of the Mitochondrial Import System in Eukaryotic Lineages.
abstract: Protein transport systems are fundamentally important for maintaining mitochondrial function. Nevertheless, mitochondrial protein translocases such as the kinetoplastid ATOM complex have recently been shown to vary in eukaryotic lineages. Various evolutionary hypotheses have been formulated to explain this diversity. To resolve any contradiction, estimating the primitive state and clarifying changes from that state are necessary. Here, we present more likely primitive models of mitochondrial translocases, specifically the translocase of the outer membrane (TOM) and translocase of the inner membrane (TIM) complexes, using scrutinized phylogenetic profiles. We then analyzed the translocases' evolution in eukaryotic lineages. Based on those results, we propose a novel evolutionary scenario for diversification of the mitochondrial transport system. Our results indicate that presequence transport machinery was mostly established in the last eukaryotic common ancestor, and that primitive translocases already had a pathway for transporting presequence-containing proteins. Moreover, secondary changes including convergent and migrational gains of a presequence receptor in TOM and TIM complexes, respectively, likely resulted from constrained evolution. The nature of a targeting signal can constrain alteration to the protein transport complex.
authors.affiliation: Artificial Intelligence Research Center, National Institute of Advanced Science and Technology (AIST), Tokyo, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Fukasawa
authors.affiliation: Artificial Intelligence Research Center, National Institute of Advanced Science and Technology (AIST), Tokyo, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Oda
authors.affiliation: Artificial Intelligence Research Center, National Institute of Advanced Science and Technology (AIST), Tokyo, Japan.|Biotechnology Research Institute for Drug Discovery, National Institute of Advanced Science and Technology (AIST), Tokyo, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Tomii
authors.affiliation: Artificial Intelligence Research Center, National Institute of Advanced Science and Technology (AIST), Tokyo, Japan.|Biotechnology Research Institute for Drug Discovery, National Institute of Advanced Science and Technology (AIST), Tokyo, Japan.
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Imai
mesh_terms: D005075:Biological Evolution; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D056890:Eukaryota / Q000235:genetics / Q000378:metabolism; D005057:Eukaryotic Cells / Q000378:metabolism; D019143:Evolution, Molecular; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000235:genetics* / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins / Q000378:metabolism; D010802:Phylogeny; D021381:Protein Transport / Q000235:genetics; D020539:Sequence Analysis, Protein / Q000379:methods
chemical_list: D002352:Carrier Proteins; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins
keywords: TIM complex; TOM complex; eukaryotes; mitochondria; protein transport