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Interaction of mammalian mitochondrial ribosomes with the inner membrane

M Liu1, L Spremulli

  • 1Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, USA.

The Journal of Biological Chemistry
|July 11, 2000
PubMed

Insights

Mitochondrial inner membranes host ribosomes involved in protein synthesis. These ribosomes associate with the membrane via electrostatic forces, not nascent polypeptide chains.

Area of Science:

  • Mitochondrial biology
  • Molecular cell biology

Background:

  • Mitochondrial protein biosynthesis produces hydrophobic proteins localized to the inner membrane.
  • This localization suggests potential synthesis on ribosomes attached to the inner membrane.

Purpose of the Study:

  • To investigate the association of ribosomes with the inner mitochondrial membrane.
  • To determine the nature of this ribosome-membrane interaction.

Main Methods:

  • Fractionation of bovine mitochondrial inner membrane and matrix.
  • Detection of ribosomal RNAs (rRNAs) using specific probes.
  • Treatment with high salt and puromycin to assess ribosome-membrane binding.

Main Results:

  • 40-50% of total ribosomes fractionated with the inner mitochondrial membrane.
  • High salt treatment released approximately half of the membrane-associated ribosomes, indicating electrostatic interactions.
  • Puromycin treatment did not release ribosomes, ruling out association via nascent polypeptide chains.
  • A subpopulation of ribosomes remained associated with detergent-insoluble membrane components.

Conclusions:

  • A significant population of ribosomes is associated with the inner mitochondrial membrane.
  • This association is primarily mediated by electrostatic forces.
  • Some ribosomes may be integrated into larger membrane complexes.

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