Interconnected assembly factors regulate the biogenesis of mitoribosomal large subunit

Area of Science:

• Mitochondrial biology
• Molecular and structural biology
• Biochemistry

Background:

• Mitoribosomes are essential for protein synthesis within mitochondria.
• Their assembly is complex, involving ribosomal RNA and proteins.
• Understanding mitoribosome biogenesis is crucial for cellular function.

Purpose of the Study:

• To investigate the biogenesis of the mitoribosomal large subunit.
• To identify and characterize assembly factors involved in this process.
• To gain insights into the structural organization of immature mitoribosomes.

Main Methods:

• Structural characterization of a stable mitoribitosomal assembly intermediate from Trypanosoma brucei.
• Analysis of mitoribosomes with altered RNA and protein composition.
• Identification of protein components and their spatial organization.

Main Results:

• A stable assembly intermediate revealed 22 mitoribosomal assembly factors, forming a large protein network (180 Å).
• This network shields the ribosomal RNA and stabilizes immature regions.
• Conserved proteins GTPBP7 and mt-EngA, along with a mitochondrial acyl-carrier protein, play specific roles in subunit assembly and maturation.
• Some identified factors have homologs in mammalian genomes.

Conclusions:

• The extensive protein network acts as a scaffold, guiding the coordinated assembly of the mitoribosomal large subunit.
• Assembly factors are progressively removed and remodeled to achieve functional mitoribosome structure.
• This study provides a detailed molecular model for mitoribosome biogenesis, highlighting conserved mechanisms.