The structural basis for release-factor activation during translation termination revealed by time-resolved cryogenic...

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• Ribosomes terminate translation upon encountering stop codons.
• Release factors (RFs) mediate stop codon recognition and peptide release.
• RFs possess distinct structural domains for codon binding and catalytic activity.

Purpose of the Study:

• To visualize the dynamic structural transitions of RFs during translation termination.
• To investigate the conformational changes of RF1 and RF2 upon ribosome binding and stop codon recognition.
• To elucidate the mechanism of RF activation on the ribosome.

Main Methods:

• Time-resolved cryo-electron microscopy (cryo-EM) was employed.
• High-resolution structures of RF1 and RF2 bound to the ribosome were determined at millisecond time points.
• Analysis of transient compact and extended RF conformations.

Main Results:

• Transient compact forms of RF1 and RF2 were observed in ribosome complexes.
• Approximately 25% of complexes exhibited RFs in a compact state at 24 ms.
• Within 60 ms, ribosome-bound RFs predominantly adopted extended conformations.

Conclusions:

• RFs exist in compact states before or during initial stop codon recognition.
• Ribosome binding and stop codon interaction induce a conformational extension of RFs.
• This dynamic structural rearrangement is crucial for efficient termination of protein synthesis.