Structure of a eukaryotic cytoplasmic pre-40S ribosomal subunit

EMBO J. 2018 Apr 3;37(7):e98499. doi: 10.15252/embj.201798499. Epub 2018 Feb 19.


Final maturation of eukaryotic ribosomes occurs in the cytoplasm and requires the sequential removal of associated assembly factors and processing of the immature 20S pre-RNA Using cryo-electron microscopy (cryo-EM), we have determined the structure of a yeast cytoplasmic pre-40S particle in complex with Enp1, Ltv1, Rio2, Tsr1, and Pno1 assembly factors poised to initiate final maturation. The structure reveals that the pre-rRNA adopts a highly distorted conformation of its 3' major and 3' minor domains stabilized by the binding of the assembly factors. This observation is consistent with a mechanism that involves concerted release of the assembly factors orchestrated by the folding of the rRNA in the head of the pre-40S subunit during the final stages of maturation. Our results provide a structural framework for the coordination of the final maturation events that drive a pre-40S particle toward the mature form capable of engaging in translation.

Keywords: cryo‐EM; pre‐40S ribosome; ribosome; ribosome assembly; ribosome biogenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cryoelectron Microscopy*
  • Cytoplasm
  • Molecular Docking Simulation*
  • Nuclear Proteins / chemistry
  • Nuclear Proteins / genetics
  • Nuclear Proteins / ultrastructure
  • Protein Conformation
  • Protein Domains
  • Protein Interaction Domains and Motifs
  • Protein Serine-Threonine Kinases / ultrastructure
  • RNA Folding
  • RNA, Ribosomal / chemistry
  • RNA, Ribosomal / ultrastructure
  • RNA-Binding Proteins / chemistry
  • RNA-Binding Proteins / ultrastructure
  • Ribosomal Proteins / chemistry
  • Ribosomal Proteins / genetics
  • Ribosomal Proteins / isolation & purification
  • Ribosomal Proteins / ultrastructure*
  • Ribosome Subunits, Small, Eukaryotic / chemistry
  • Ribosome Subunits, Small, Eukaryotic / genetics
  • Ribosome Subunits, Small, Eukaryotic / ultrastructure*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / ultrastructure*
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / isolation & purification
  • Saccharomyces cerevisiae Proteins / ultrastructure*


  • ENP1 protein, S cerevisiae
  • LTV1 protein, S cerevisiae
  • NOB1 protein, S cerevisiae
  • Nuclear Proteins
  • PNO1 protein, S cerevisiae
  • RNA, Ribosomal
  • RNA-Binding Proteins
  • RPS21A protein, S cerevisiae
  • Ribosomal Proteins
  • Saccharomyces cerevisiae Proteins
  • Protein Serine-Threonine Kinases
  • Rio2 protein, S cerevisiae