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The role of Tim9p in the assembly of the TIM22 import complexes

Danielle Leuenberger1, Sean P Curran, David Wong

  • 1Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095-1569, USA.

Traffic (Copenhagen, Denmark)
|March 27, 2003
PubMed

Insights

Mutations in the Tim9p protein disrupt mitochondrial protein import by affecting the assembly of essential protein complexes. These findings highlight the importance of the

Area of Science:

  • Mitochondrial biology
  • Protein import machinery
  • Molecular genetics

Background:

  • The TIM22 protein import system is crucial for inserting proteins into the mitochondrial inner membrane.
  • Tim9p is a component of both soluble and membrane-bound complexes within this system.
  • Understanding Tim9p function is key to deciphering mitochondrial protein trafficking.

Purpose of the Study:

  • To investigate the role of the 'twin CX3C' motif in Tim9p function.
  • To characterize the impact of mutations near this motif on mitochondrial protein import.
  • To elucidate the assembly requirements for Tim9p-containing complexes.

Main Methods:

  • Analysis of temperature-sensitive mutants (tim9-3 and tim9-19).
  • Biochemical assessment of mitochondrial protein import and complex assembly.
  • In vitro studies of Tim9p and Tim10p complex formation.

Main Results:

  • Mutations near the 'twin CX3C' motif in Tim9p severely impaired mitochondrial protein import and complex assembly in tim9-3.
  • The tim9-19 mutation affected the soluble Tim9p-Tim10p complex but not the membrane complex, leading to a moderate decrease in import.
  • Tim9p and Tim10p failed to assemble into a complex when coexpressed, indicating specific assembly requirements.

Conclusions:

  • Residues near the 'twin CX3C' motif are critical for Tim9p assembly into both soluble and membrane-bound mitochondrial import complexes.
  • Proper assembly of Tim9p is essential for efficient protein import into the mitochondrial inner membrane.
  • The study provides insights into the structural and functional importance of the conserved 'twin CX3C' motif in small Tim proteins.

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