2008/10/31

Cryo-electron microscopy shows ribosomes on the move.

Researchers from the Structural Biology Unit of CICbioGUNE have captured the structure of ribosomes during the movement of tRNAs. The study performed using cryo-EM analysis shows that ribosomes oscillate between two distinct conformations: a classical state with tRNAs residing in aminoacyl (A) and peptidyl (P) sites; and a ratcheted arrangement where tRNAs adopt hybrid A/P and P/E (E, exit site) positions.

The existence of the two different structural states was confirmed using maximum-likelihood based classification procedure within a population of ribosomes. The findings describe how the relative rotation between the two ribosomal subunits promotes the movement of tRNAs without the participation of elongation factors. Such a universal mechanism would explain the importance of the common two-unit ribosome design in the process of protein translation.

The work has been carried out in collaboration with researchers from the National Center for Biotechnology (CNB-CSIC) and the Max Plank Institute for Biophysical Chemistry.

Figure: rendering of cryo-EM maps of ribosomes in the classic (left) and hybrid (right) states. Ribosomal subunits have been separated to allow visualization of tRNAs in the inter-subunit cavity.