title: Protein translocation channel of mitochondrial inner membrane and matrix-exposed import motor communicate via two-domain coupling protein.
abstract: The majority of mitochondrial proteins are targeted to mitochondria by N-terminal presequences and use the TIM23 complex for their translocation across the mitochondrial inner membrane. During import, translocation through the channel in the inner membrane is coupled to the ATP-dependent action of an Hsp70-based import motor at the matrix face. How these two processes are coordinated remained unclear. We show here that the two domain structure of Tim44 plays a central role in this process. The N-terminal domain of Tim44 interacts with the components of the import motor, whereas its C-terminal domain interacts with the translocation channel and is in contact with translocating proteins. Our data suggest that the translocation channel and the import motor of the TIM23 complex communicate through rearrangements of the two domains of Tim44 that are stimulated by translocating proteins.
authors.affiliation: Biomedical Center Munich, Department of Physiological Chemistry, Ludwig-Maximilians-Universität, Munich, Germany.
authors.forename: Rupa
authors.initials: R
authors.lastname: Banerjee
authors.affiliation: Biomedical Center Munich, Department of Physiological Chemistry, Ludwig-Maximilians-Universität, Munich, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Gladkova
authors.affiliation: Biomedical Center Munich, Department of Physiological Chemistry, Ludwig-Maximilians-Universität, Munich, Germany.
authors.forename: Koyeli
authors.initials: K
authors.lastname: Mapa
authors.affiliation: Gene Center, Department of Biochemistry, Ludwig-Maximilians-Universität, Munich, Germany.
authors.forename: Gregor
authors.initials: G
authors.lastname: Witte
authors.affiliation: Biomedical Center Munich, Department of Physiological Chemistry, Ludwig-Maximilians-Universität, Munich, Germany.
authors.forename: Dejana
authors.initials: D
authors.lastname: Mokranjac
mesh_terms: D026901:Membrane Transport Proteins / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism*; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D008954:Models, Biological; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: 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; C077016:TIM44 protein, S cerevisiae
keywords: E. coli; Hsp70; S. cerevisiae; TIM23; biochemistry; cell biology; mitochondria; protein translocation/sorting