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Assessment of Submitochondrial Protein Localization in Budding Yeast Saccharomyces cerevisiae
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Integral membrane proteins in the mitochondrial outer membrane of Saccharomyces cerevisiae

Lena Burri1, Katherine Vascotto, Ian E Gentle

  • 1Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Australia.

The FEBS Journal
|May 13, 2006
PubMed

Insights

Mitochondria outer membrane proteins, unlike their bacterial ancestors, often use alpha-helical structures. The novel Om14 protein, a new alpha-helical outer membrane protein, requires the translocase complex for insertion.

Area of Science:

  • Mitochondrial biology
  • Protein biophysics
  • Cellular and molecular biology

Background:

  • Mitochondria originated from a bacterial endosymbiont, with outer membrane proteins expected to be beta-barrel structured.
  • Proteomics of yeast mitochondria outer membrane indicates most integral proteins possess alpha-helical transmembrane domains, not beta-barrels.
  • While often predicted with a single transmembrane segment, more complex topologies exist for these proteins.

Purpose of the Study:

  • To characterize the novel outer membrane protein Om14.
  • To determine the structure and insertion mechanism of Om14.
  • To investigate the regulation of Om14 expression.

Main Methods:

  • Protein purification and sequencing of Om14.
  • Analysis of gene transcription and protein levels under different growth conditions.
  • Hydropathy prediction and limited protease digestion to determine transmembrane topology.

Main Results:

  • Om14 is encoded by the YBR230c gene, with an spliced intron.
  • Om14 expression and protein levels are significantly lower in glucose-grown cells compared to non-fermentable carbon sources.
  • Hydropathy analysis and protease digestion revealed Om14 has three alpha-helical transmembrane segments.
  • Om14 requires the outer mitochondrial membrane translocase complex for insertion.

Conclusions:

  • Mitochondrial outer membrane proteins with alpha-helical structures represent functions acquired post-endosymbiosis.
  • Om14 exemplifies a novel class of alpha-helical outer membrane proteins.
  • The insertion of these proteins relies on the specific mitochondrial outer membrane translocase machinery.

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