Molecular Insights Revealing Interaction of Tim23 and Channel Subunits of Presequence Translocase

Mol Cell Biol. 2013 Dec;33(23):4641-59. doi: 10.1128/MCB.00876-13. Epub 2013 Sep 23.

Abstract

Tim23 is an essential channel-forming subunit of the presequence translocase recruiting multiple components for assembly of the core complex, thereby regulating the protein translocation process. However, understanding of the precise interaction of subunits associating with Tim23 remains largely elusive. Our findings highlight that transmembrane helix 1 (TM1) is required for homodimerization of Tim23, while, together with TM2, it is involved in preprotein binding within the channel. Based on our evidence, we predict that the TM1 and TM2 from each dimer are involved in the formation of the central translocation pore, aided by Tim17. Furthermore, TM2 is also involved in the recruitment of Tim21 and the presequence-associated motor (PAM) subcomplex to the Tim23 channel, while the matrix-exposed loop L1 generates specificity in their association with the core complex. Strikingly, our findings indicate that the C-terminal sequence of Tim23 is dispensable for growth and functions as an inhibitor for binding of Tim21. Our model conceptually explains the cooperative function between Tam41 and Pam17 subunits, while the antagonistic activity of Tim21 predominantly determines the bound and free forms of the PAM subcomplex during import.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Half-Life
  • Membrane Potentials
  • Membrane Transport Proteins / chemistry
  • Membrane Transport Proteins / metabolism*
  • Mitochondrial Membrane Transport Proteins / metabolism
  • Peptidyl Transferases / metabolism*
  • Protein Interaction Domains and Motifs
  • Protein Interaction Mapping
  • Protein Multimerization
  • Protein Structure, Secondary
  • Protein Subunits / metabolism
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / metabolism*

Substances

  • Membrane Transport Proteins
  • Mitochondrial Membrane Transport Proteins
  • Protein Subunits
  • Saccharomyces cerevisiae Proteins
  • TIM17 protein, S cerevisiae
  • TIM23 protein, S cerevisiae
  • Tim21 protein, S cerevisiae
  • Peptidyl Transferases