title: Role of Tom5 in maintaining the structural stability of the TOM complex of mitochondria.
abstract: Transport of nuclear encoded proteins into mitochondria is mediated by multisubunit translocation machineries in the outer and inner membranes of mitochondria. The TOM complex contains receptor and pore components that facilitate the recognition of preproteins and their transfer through the outer membrane. In addition, the complex contains a set of small proteins. Tom7 and Tom6 have been found in Neurospora and yeast, Tom5 has been found so far only in the latter organism. In the present study, we identified Neurospora Tom5 and analyzed its function in comparison to yeast Tom5, which has been proposed to play a role as a receptor-like component. Neurospora Tom5 crosses the outer membrane with its carboxyl terminus facing the intermembrane space like the other small Tom components. The temperature-sensitive growth phenotype of the yeast TOM5 deletion was rescued by overexpression of Neurospora Tom5. On the other hand, Neurospora cells deficient in tom5 did not exhibit any defect in growth. The structural stability of TOM complexes from cells devoid of Tom5 was significantly altered in yeast but not in Neurospora. The efficiency of protein import in Neurospora mitochondria was not affected by deletion of tom5, whereas in yeast it was reduced as compared with wild type. We conclude that the main role of Tom5, rather than being a receptor, is maintaining the structural integrity of the TOM complex.
authors.affiliation: Adolf-Butenandt-Institut für Physiologische Chemie, Ludwig-Maximilians-Universität München, 81377 München, Germany.
authors.forename: Simone
authors.initials: S
authors.lastname: Schmitt
authors.forename: Uwe
authors.initials: U
authors.lastname: Ahting
authors.forename: Lutz
authors.initials: L
authors.lastname: Eichacker
authors.forename: Bernhard
authors.initials: B
authors.lastname: Granvogl
authors.forename: Nancy E
authors.initials: NE
authors.lastname: Go
authors.forename: Frank E
authors.initials: FE
authors.lastname: Nargang
authors.forename: Walter
authors.initials: W
authors.lastname: Neupert
authors.forename: Stephan
authors.initials: S
authors.lastname: Nussberger
mesh_terms: D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D001483:Base Sequence; D049109:Cell Proliferation; D002845:Chromatography; D003001:Cloning, Molecular; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D017353:Gene Deletion; D015151:Immunoblotting; D013058:Mass Spectrometry; D026901:Membrane Transport Proteins / Q000737:chemistry; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism / Q000502:physiology*; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D008969:Molecular Sequence Data; D009492:Neurospora crassa / Q000378:metabolism*; D009685:Nuclear Envelope / Q000378:metabolism; D022022:Nuclear Pore / Q000378:metabolism; D010641:Phenotype; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D013696:Temperature; D013997:Time Factors
chemical_list: D003432:Cross-Linking Reagents; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D029701:Saccharomyces cerevisiae Proteins; C083081:TIM23 protein, S cerevisiae; C106794:TOM5 protein, S cerevisiae