Protein import into mitochondria.
Most mitochondrial proteins are encoded by the nuclear genome and thus have to be imported into mitochondria from the cytosol. Protein translocation across and into the mitochondrial membranes is a multistep process facilitated by the coordinated action of at least four specialized translocation systems in the outer and inner membranes of mitochondria. The outer membrane contains one general translocase, the TOM complex, whereas three distinct translocases are located in the inner membrane, which facilitates translocation of different classes of preproteins. The TIM23 complex mediates import of matrix-targeted preproteins with N-terminal presequences, whereas hydrophobic preproteins with internal targeting signals are inserted into the inner membrane via the TIM22 complex. The OXA translocase mediates the insertion of preproteins from the matrix space into the inner membrane. This review focuses on the structural organization and function of the import machinery of the model organisms of Saccharomyces cerevisiae and Neurospora crassa. In addition, the molecular basis of a new human mitochondrial disorder is discussed, the Mohr-Tranebjaerg syndrome. This is the first known disease, which is caused by an impaired mitochondrial protein import machinery leading to progressive neurodegeneration.
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Adolf-Butenandt-Institut für Physiologische Chemie, Ludwig-Maximilians Universität München, Germany.
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D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins / Q000378:metabolism*; D021381:Protein Transport; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D015398:Signal Transduction
D002352:Carrier 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; D029701:Saccharomyces cerevisiae Proteins; C107250:TIM10 protein, S cerevisiae; C100674:TIM12 protein, S cerevisiae; C083081:TIM23 protein, S cerevisiae; C116366:Tim9 protein, S cerevisiae