Interaction of the J-protein heterodimer Pam18/Pam16 of the mitochondrial import motor with the translocon of the inner membrane

Mol Biol Cell. 2008 Jan;19(1):424-32. doi: 10.1091/mbc.e07-08-0748. Epub 2007 Nov 14.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Dimerization
  • Membrane Transport Proteins / chemistry
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism*
  • Mitochondria / metabolism*
  • Mitochondrial Membrane Transport Proteins
  • Mitochondrial Membranes / metabolism*
  • Molecular Motor Proteins / metabolism*
  • Mutation / genetics
  • Protein Binding
  • Protein Structure, Tertiary
  • Protein Transport
  • Recombinant Fusion Proteins / metabolism
  • Saccharomyces cerevisiae / cytology
  • Saccharomyces cerevisiae / growth & development
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Suppression, Genetic

Substances

  • Membrane Transport Proteins
  • Mitochondrial Membrane Transport Proteins
  • Molecular Motor Proteins
  • PAM18 J protein, S cerevisiae
  • Pam16 protein, S cerevisiae
  • Recombinant Fusion Proteins
  • Saccharomyces cerevisiae Proteins