The ribosome receptors Mrx15 and Mba1 jointly organize cotranslational insertion and protein biogenesis in mitochondria

Area of Science:

• Mitochondrial biology
• Molecular cell biology
• Protein biogenesis

Background:

• Mitochondrial gene expression produces essential oxidative phosphorylation subunits.
• These hydrophobic proteins require cotranslational insertion into the inner mitochondrial membrane.
• Membrane insertion occurs on mitochondrial ribosomes.

Purpose of the Study:

• To identify novel factors involved in mitochondrial cotranslational protein insertion.
• To elucidate the mechanism of membrane protein biogenesis in mitochondria.

Main Methods:

• Systematic mass spectrometry-based proteomic approach.
• Identification and characterization of novel interacting partners of mitochondrial ribosomes.

Main Results:

• Discovery of a previously uncharacterized membrane protein, Mrx15.
• Mrx15 interacts with the large ribosomal subunit via its C-terminal domain.
• Mrx15 contacts nascent mitochondrial translation products.
• Mrx15 and Mba1 play overlapping roles in cotranslational protein insertion.

Conclusions:

• Mrx15 is a novel ribosome receptor involved in mitochondrial membrane protein biogenesis.
• Ribosome receptors like Mrx15 and Mba1 organize the cotranslational insertion of proteins into the mitochondrial inner membrane.
• This study reveals a new mechanism for organizing mitochondrial membrane protein biogenesis.