Mitochondrial ribosomes manufacture 13 proteins, all of...

Name: Problem 18, Chapter 27: Fundamentals of Biochemistry
Uploaded: 2021-03-26T08:45:48-08:00
Duration: 1 min 4 s
Channel: Shazia Naz
Description: Mitochondrial ribosomes manufacture 13 proteins, all of which are components of the oxidative phosphorylation machinery. Propose an explanation why the peptide exit tunnel of the mitoribosome is lined with hydrophobic groups rather than hydrophilic groups, as in a cytosplasmic ribosome.

Mitochondrial ribosomes manufacture 13 proteins, all of which are components of the oxidative phosphorylation machinery. Propose an explanation why the peptide exit tunnel of the mitoribosome is lined with hydrophobic groups rather than hydrophilic groups, as in a cytosplasmic ribosome.

Key Concepts

Mitochondrial Protein Synthesis

Mitochondria have their own machinery to produce a specific subset of proteins that are crucial for the energy production process. These proteins, many of which are embedded in the inner mitochondrial membrane, are synthesized within the organelle, requiring specialized adaptations of the mitochondrial ribosome to accommodate their unique biochemical properties.

Peptide Exit Tunnel Structure

The peptide exit tunnel of a ribosome is the path through which a newly forming polypeptide chain emerges. In mitochondrial ribosomes, this tunnel is made to present a hydrophobic environment, which is a specialized feature that differs from the typically hydrophilic tunnel found in cytosolic ribosomes.

Hydrophobic Environment for Nascent Chains

Proteins involved in oxidative phosphorylation often have multiple hydrophobic transmembrane domains. A hydrophobic peptide exit tunnel helps stabilize these hydrophobic regions as they emerge from the ribosome, preventing misfolding or aggregation in the aqueous mitochondrial matrix and facilitating their proper insertion into the inner mitochondrial membrane.

Membrane Protein Integration

The synthesis of membrane proteins often involves a coordinated process where translation and membrane insertion are coupled. The hydrophobic lining of the mitochondrial peptide exit tunnel is an adaptation that enhances the efficiency of inserting nascent polypeptides into a similarly hydrophobic membrane environment, ensuring correct folding and functional integration.

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