Mitoribosomal small subunit biogenesis in trypanosomes involves an extensive assembly machinery

Science. 2019 Sep 13;365(6458):1144-1149. doi: 10.1126/science.aaw5570.


Mitochondrial ribosomes (mitoribosomes) are large ribonucleoprotein complexes that synthesize proteins encoded by the mitochondrial genome. An extensive cellular machinery responsible for ribosome assembly has been described only for eukaryotic cytosolic ribosomes. Here we report that the assembly of the small mitoribosomal subunit in Trypanosoma brucei involves a large number of factors and proceeds through the formation of assembly intermediates, which we analyzed by using cryo-electron microscopy. One of them is a 4-megadalton complex, referred to as the small subunit assemblosome, in which we identified 34 factors that interact with immature ribosomal RNA (rRNA) and recognize its functionally important regions. The assembly proceeds through large-scale conformational changes in rRNA coupled with successive incorporation of mitoribosomal proteins, providing an example for the complexity of the ribosomal assembly process in mitochondria.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cryoelectron Microscopy
  • Mitochondrial Proteins / ultrastructure*
  • Mitochondrial Ribosomes / ultrastructure*
  • Models, Molecular
  • Nucleic Acid Conformation
  • Protein Structure, Quaternary
  • RNA Interference
  • RNA Stability
  • RNA, Ribosomal / ultrastructure*
  • Ribosomal Proteins / ultrastructure*
  • Trypanosoma brucei brucei / chemistry*


  • Mitochondrial Proteins
  • RNA, Ribosomal
  • Ribosomal Proteins