Conformation transitions of eukaryotic polyribosomes during multi-round translation

Nucleic Acids Res. 2015 Jan;43(1):618-28. doi: 10.1093/nar/gku1270. Epub 2014 Dec 17.


Using sedimentation and cryo electron tomography techniques, the conformations of eukaryotic polyribosomes formed in a long-term cell-free translation system were analyzed over all the active system lifetime (20-30 translation rounds during 6-8 h in wheat germ extract at 25°C). Three distinct types of the conformations were observed: (i) circular polyribosomes, varying from ring-shaped forms to circles collapsed into double rows, (ii) linear polyribosomes, tending to acquire planar zigzag-like forms and (iii) densely packed 3D helices. At the start, during the first two rounds of translation mostly the circular (ring-shaped and double-row) polyribosomes and the linear (free-shaped and zigzag-like) polyribosomes were formed ('juvenile phase'). The progressive loading of the polyribosomes with translating ribosomes induced the opening of the circular polyribosomes and the transformation of a major part of the linear polyribosomes into the dense 3D helices ('transitional phase'). After 2 h from the beginning (about 8-10 rounds of translation) this compact form of polyribosomes became predominant, whereas the circular and linear polyribosome fractions together contained less than half of polysomal ribosomes ('steady-state phase'). The latter proportions did not change for several hours. Functional tests showed a reduced translational activity in the fraction of the 3D helical polyribosomes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell-Free System
  • Cryoelectron Microscopy
  • Models, Molecular
  • Polyribosomes / chemistry*
  • Protein Biosynthesis*
  • RNA, Messenger / chemistry


  • RNA, Messenger