Partial spontaneous intersubunit rotations in pretranslocation ribosomes.

Area of Science:

• Molecular Biology
• Biophysics

Background:

• Ribosome function involves two key steps: peptidyl transfer and translocation.
• These steps are associated with distinct rotations between the large and small ribosomal subunits.

Purpose of the Study:

• To investigate the spontaneous conformational dynamics of ribosomes during translation.
• To reconcile conflicting previous findings on ribosome rotations before translocation.

Main Methods:

• High-speed single-molecule microscopy was employed to track ribosome dynamics in real time.
• Ribosomes were labeled at rRNA helices h44 and H101 for precise monitoring.

Main Results:

• Peptidyl transfer was shown to unlock spontaneous rotations in ribosomes.
• Pretranslocation ribosomes, labeled at h44-H101, exhibited spontaneous exchange between three rotational states.
• These spontaneous rotations were observed to be restricted prior to aminoacyl-tRNA binding.

Conclusions:

• Peptidyl transfer facilitates spontaneous ribosome rotations, allowing pretranslocation states to access multiple conformations.
• The findings support the Brownian motion model for ribosome translocation during protein synthesis.