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Genetic and functional interactions between the mitochondrial outer membrane proteins Tom6 and Sam37

Jovana Dukanovic1, Kai S Dimmer, Nathalie Bonnefoy

  • 1Interfaculty Institute for Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany.

Molecular and Cellular Biology
|October 3, 2009
PubMed

Insights

The mitochondrial SAM/TOB complex protein Sam37 interacts with Tom6, crucial for beta-barrel protein biogenesis. This interaction is vital for cell growth at higher temperatures, highlighting Sam37

Area of Science:

  • Mitochondrial protein import and biogenesis
  • Outer mitochondrial membrane protein insertion
  • Protein complex interactions

Background:

  • The TOM complex facilitates general mitochondrial protein entry.
  • The SAM/TOB complex integrates beta-barrel proteins into the outer mitochondrial membrane.
  • Sam37 is a core component of the SAM/TOB complex, essential for growth at elevated temperatures, but its function is unclear.

Purpose of the Study:

  • To identify Sam37 interacting partners and elucidate its function.
  • To investigate the functional relationship between Sam37 and the TOM complex.

Main Methods:

  • Screening for multicopy suppressors of sam37 deletion (sam37Δ).
  • Genetic interaction studies between SAM37 and TOM complex components.
  • Analysis of cell viability and growth phenotypes under varying temperature conditions.

Main Results:

  • Tom6, a small subunit of the TOM complex, was identified as a multicopy suppressor of sam37Δ.
  • A tight genetic interaction was observed between Sam37 and Tom6; simultaneous deletion is lethal.
  • Overexpression of Sam37 rescues the growth defect of tom6Δ, and Tom6 stabilizes Tom40, a key beta-barrel protein.

Conclusions:

  • Sam37 is required for optimal growth at higher temperatures, likely by enhancing the biogenesis of the essential beta-barrel protein Tom40.
  • The function of Sam37 in Tom40 biogenesis can be compensated by increased Tom40 stability mediated by Tom6.
  • This study reveals a functional link between the SAM/TOB and TOM complexes, crucial for mitochondrial outer membrane protein biogenesis.

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