title: Mitochondrial protein import motor: differential role of Tim44 in the recruitment of Pam17 and J-complex to the presequence translocase.
abstract: The presequence translocase of the mitochondrial inner membrane (TIM23 complex) mediates the import of preproteins with amino-terminal presequences. To drive matrix translocation the TIM23 complex recruits the presequence translocase-associated motor (PAM) with the matrix heat shock protein 70 (mtHsp70) as central subunit. Activity and localization of mtHsp70 are regulated by four membrane-associated cochaperones: the adaptor protein Tim44, the stimulatory J-complex Pam18/Pam16, and Pam17. It has been proposed that Tim44 serves as molecular platform to localize mtHsp70 and the J-complex at the TIM23 complex, but it is unknown how Pam17 interacts with the translocase. We generated conditional tim44 yeast mutants and selected a mutant allele, which differentially affects the association of PAM modules with TIM23. In tim44-804 mitochondria, the interaction of the J-complex with the TIM23 complex is impaired, whereas unexpectedly the binding of Pam17 is increased. Pam17 interacts with the channel protein Tim23, revealing a new interaction site between TIM23 and PAM. Thus, the motor PAM is composed of functional modules that bind to different sites of the translocase. We suggest that Tim44 is not simply a scaffold for binding of motor subunits but plays a differential role in the recruitment of PAM modules to the inner membrane translocase.
authors.affiliation: Institut für Biochemie und Molekularbiologie, ZBMZ, Germany.
authors.forename: Dana P
authors.initials: DP
authors.lastname: Hutu
authors.forename: Bernard
authors.initials: B
authors.lastname: Guiard
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Chacinska
authors.forename: Dorothea
authors.initials: D
authors.lastname: Becker
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Pfanner
authors.forename: Peter
authors.initials: P
authors.lastname: Rehling
authors.forename: Martin
authors.initials: M
authors.lastname: van der Laan
mesh_terms: D003432:Cross-Linking Reagents / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism*; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins / Q000378:metabolism*; D020409:Molecular Motor Proteins / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism*; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D011498:Protein Precursors / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D013696:Temperature
chemical_list: D003432:Cross-Linking Reagents; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D020409:Molecular Motor Proteins; D046912:Multiprotein Complexes; D050505:Mutant Proteins; C503873:Pam17 protein, S cerevisiae; D011498:Protein Precursors; D029701:Saccharomyces cerevisiae Proteins; C083081:TIM23 protein, S cerevisiae; C077016:TIM44 protein, S cerevisiae