Molecular determinants of release factor 2 for ArfA-mediated ribosome rescue

Area of Science:

• Molecular Biology
• Bacterial Protein Synthesis
• Ribosome Function

Background:

• Translation termination typically requires stop codons recognized by release factors RF1 or RF2.
• Absence of stop codons stalls ribosomes, preventing normal protein release.
• In Escherichia coli, ArfA facilitates stop codon-independent polypeptide release with RF2.

Purpose of the Study:

• To identify regions of RF2 crucial for ArfA-mediated ribosome rescue.
• To understand the molecular basis for RF2's specific interaction with the ArfA-ribosome complex.
• To elucidate the mechanism of stop codon-independent translation termination.

Main Methods:

• Investigated RF2 regions interacting with ArfA using mutagenesis.
• Assessed RF1 and modified RF1 ability to associate with ArfA-ribosome complex.
• Identified key residues for peptidyl-tRNA hydrolysis after ribosome binding.

Main Results:

• Specific hydrophobic residues at the RF2-ArfA interface are essential for complex formation.
• Introducing these residues into RF1 partially restored ArfA binding but not hydrolysis.
• WT RF1 did not associate with the ArfA-ribosome complex.
• Key residues mediating post-binding events were identified.

Conclusions:

• RF2's unique structural features at the ArfA interface dictate its specific recognition by the ArfA-ribosome complex.
• RF2 undergoes conformational changes upon binding to facilitate stop codon-independent polypeptide release.
• These findings clarify the mechanism of bacterial ribosome rescue.