Mitoribosomal small subunit biogenesis in trypanosomes involves an extensive assembly machinery

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Mitochondrial ribosomes (mitoribosomes) synthesize proteins encoded by the mitochondrial genome.
• The assembly machinery for eukaryotic cytosolic ribosomes is well-characterized, but mitochondrial ribosome assembly is less understood.
• Mitoribosomes are essential for cellular respiration and mitochondrial function.

Purpose of the Study:

• To investigate the assembly process of the small mitochondrial ribosomal subunit in Trypanosoma brucei.
• To identify factors and intermediates involved in mitoribosome biogenesis.
• To elucidate the structural and dynamic aspects of mitoribosome assembly.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was used to analyze assembly intermediates.
• Biochemical techniques were employed to identify interacting factors.
• Structural analysis of the small mitoribosomal subunit assemblosome.

Main Results:

• The assembly of the small mitoribosomal subunit in Trypanosoma brucei involves a large number of factors.
• A 4-megadalton complex, the small subunit assemblosome, was identified as a key intermediate.
• 34 factors were identified interacting with immature ribosomal RNA (rRNA) within the assemblosome, recognizing functionally important rRNA regions.
• Assembly proceeds via large-scale rRNA conformational changes and stepwise protein incorporation.

Conclusions:

• Mitochondrial ribosome assembly is a complex process involving numerous factors and distinct intermediates.
• The identified assemblosome provides a structural snapshot of early mitoribosome biogenesis.
• This study offers a model for understanding the intricate mechanisms of mitochondrial ribosome assembly.