title: Interaction of the J-protein heterodimer Pam18/Pam16 of the mitochondrial import motor with the translocon of the inner membrane.
abstract: Import of proteins across the inner mitochondrial membrane through the Tim23:Tim17 translocase requires the function of an essential import motor having mitochondrial 70-kDa heat-shock protein (mtHsp70) at its core. The heterodimer composed of Pam18, the J-protein partner of mtHsp70, and the related protein Pam16 is a critical component of this motor. We report that three interactions contribute to association of the heterodimer with the translocon: the N terminus of Pam16 with the matrix side of the translocon, the inner membrane space domain of Pam18 (Pam18(IMS)) with Tim17, and the direct interaction of the J-domain of Pam18 with the J-like domain of Pam16. Pam16 plays a major role in translocon association, as alterations affecting the stability of the Pam18:Pam16 heterodimer dramatically affect association of Pam18, but not Pam16, with the translocon. Suppressors of the growth defects caused by alterations in the N terminus of Pam16 were isolated and found to be due to mutations in a short segment of TIM44, the gene encoding the peripheral membrane protein that tethers mtHsp70 to the translocon. These data suggest a model in which Tim44 serves as a scaffold for precise positioning of mtHsp70 and its cochaperone Pam18 at the translocon.
authors.affiliation: Department of Biochemistry, University of Wisconsin, Madison, Madison, WI 53706, USA.
authors.forename: Patrick R
authors.initials: PR
authors.lastname: D'Silva
authors.forename: Brenda
authors.initials: B
authors.lastname: Schilke
authors.forename: Masaya
authors.initials: M
authors.lastname: Hayashi
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Craig
mesh_terms: D019281:Dimerization; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D051336:Mitochondrial Membranes / Q000378:metabolism*; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D020409:Molecular Motor Proteins / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013489:Suppression, Genetic
chemical_list: D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D020409:Molecular Motor Proteins; C480348:PAM18 J protein, S cerevisiae; C484526:Pam16 protein, S cerevisiae; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins