title: The mitochondrial import machinery for preproteins.
abstract: Most mitochondrial proteins are transported from the cytosol into the organelle. Due to the division of mitochondria into an outer and inner membrane, an intermembrane space and a matrix, an elaborated system for recognition and transport of preproteins has evolved. The translocase of the outer mitochondrial membrane (TOM) and the translocases of the inner mitochondrial membrane (TIM) mediate these processes. Receptor proteins on the cytosolic face of mitochondria recognize the cargo proteins and transfer them to the general import pore (GIP) of the outer membrane. Following the passage of preproteins through the outer membrane they are transported with the aid of the TIM23 complex into either the matrix, inner membrane, or intermembrane space. Some preprotein families utilize the TIM22 complex for their insertion into the inner membrane. The identification of protein components, which are involved in these transport processes, as well as significant insights into the molecular function of some of them, has been achieved in recent years. Moreover, we are now approaching a new era in which elaborated techniques have already allowed and will enable us to gather information about the TOM and TIM complexes on an ultrastructural level.
authors.affiliation: Institut für Biochemie and Molekularbiologie, Universität Freiburg, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Rehling
authors.forename: N
authors.initials: N
authors.lastname: Wiedemann
authors.forename: N
authors.initials: N
authors.lastname: Pfanner
authors.forename: K N
authors.initials: KN
authors.lastname: Truscott
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D005656:Fungal Proteins / Q000502:physiology; D018840:HSP70 Heat-Shock Proteins / Q000502:physiology; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D046911:Macromolecular Substances; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000502:physiology; D026901:Membrane Transport Proteins / Q000502:physiology; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D008954:Models, Biological; D008969:Molecular Sequence Data; D009492:Neurospora crassa / Q000378:metabolism; D018272:Porins / Q000502:physiology; D011498:Protein Precursors / Q000378:metabolism*; D021382:Protein Sorting Signals; D021381:Protein Transport / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000502:physiology; D050994:Voltage-Dependent Anion Channels
chemical_list: D002352:Carrier Proteins; D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D018272:Porins; D011498:Protein Precursors; D021382:Protein Sorting Signals; D029701:Saccharomyces cerevisiae Proteins; C102549:TIM22 protein, S cerevisiae; C083081:TIM23 protein, S cerevisiae; C077016:TIM44 protein, S cerevisiae; C489671:TIMM44 protein, human; C106794:TOM5 protein, S cerevisiae; C099634:TOM7 protein, S cerevisiae; C066555:Tom40 protein, S cerevisiae; C429542:Tom6 protein, Neurospora crassa; D050994:Voltage-Dependent Anion Channels