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The m-AAA protease processes cytochrome c peroxidase preferentially at the inner boundary membrane of mitochondria

Ida E Suppanz1, Christian A Wurm, Dirk Wenzel

  • 1Department of NanoBiophotonics/Mitochondrial Structure and Dynamics, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.

Molecular Biology of the Cell
|November 21, 2008
PubMed

Insights

The mitochondrial m-AAA protease and its substrate Ccp1 localize to the inner boundary membrane (IBM). This suggests the IBM is a key site for protein quality control and activation, distinct from the cristae membrane (CM).

Area of Science:

  • Mitochondrial biology
  • Cellular protein homeostasis
  • Membrane protein complexes

Background:

  • Mitochondrial inner membrane is compartmentalized into inner boundary membrane (IBM) and cristae membrane (CM).
  • Functional differences between IBM and CM remain largely unknown.
  • The m-AAA protease is a vital hetero-oligomeric complex in the mitochondrial inner membrane.

Purpose of the Study:

  • To investigate the sub-compartmental localization of the m-AAA protease and its substrate, cytochrome c peroxidase (Ccp1), within yeast mitochondria.
  • To explore potential functional distinctions between the mitochondrial inner boundary membrane (IBM) and cristae membrane (CM).

Main Methods:

  • Live cell fluorescence microscopy in yeast.
  • Quantitative immunoelectron microscopy.
  • Analysis of m-AAA protease and Ccp1 localization.

Main Results:

  • The m-AAA protease shows preferential localization to the IBM.
  • The precursor form of Ccp1 accumulates in the IBM when the m-AAA protease is non-functional.
  • Mature Ccp1 translocates to the cristae space only after cleavage by the m-AAA protease.

Conclusions:

  • Protein quality control and proteolytic activation by the m-AAA protease occur predominantly in the IBM.
  • These findings highlight significant functional specialization between the IBM and CM of mitochondria.

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