Principles of mitoribosomal small subunit assembly in eukaryotes

Area of Science:

• Molecular Biology
• Structural Biology
• Cellular Metabolism

Background:

• Mitochondrial ribosomes (mitoribosomes) synthesize essential proteins for oxidative phosphorylation and ATP production.
• Mitoribosome biogenesis is critical for cellular energy metabolism and overall function.

Purpose of the Study:

• To elucidate the structural mechanisms underlying eukaryotic mitoribosome small subunit assembly.
• To investigate the roles of GTPases, rRNA folding, and mitoribosomal proteins in early assembly steps.
• To compare conserved and species-specific assembly principles between yeast and human mitoribosomes.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was employed to determine nine structures.
• Analysis of native yeast and human mitoribosomal small subunit assembly intermediates.

Main Results:

• Detailed structures of nine assembly intermediates reveal mechanistic insights into GTPase function in decoding center formation.
• The study illuminates how initial rRNA folding, processing, and the active roles of mitoribosomal proteins occur during assembly.
• Structural intermediates from yeast and humans highlight conserved and divergent pathways in eukaryotic mitoribosome maturation.

Conclusions:

• Structural dynamics between assembly factors, proteins, and rRNA are essential for functional mitoribosome subunit generation.
• The findings provide a model for the evolution of complexity and diversity in large ribonucleoprotein assemblies.
• This work deepens our understanding of mitoribosome biogenesis, essential for ATP production and cellular health.