Thermodynamic and kinetic insights into stop codon recognition by release factor 1

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Translation termination relies on class I release factors (RF1/RF2) recognizing stop codons.
• Stop codon recognition involves hydrogen bonds and stacking interactions with conserved residues in RF1/RF2 domain II.
• RF1 positioning on the ribosome is thought to be coupled with stop codon recognition for efficient peptide release.

Purpose of the Study:

• To investigate the role of four conserved residues (Gln185, Arg186, Thr190, Thr198) in Escherichia coli RF1.
• To determine if these residues are critical for discriminating stop codons from sense codons.
• To assess the impact of mutations on RF1 binding to the ribosome and peptide release.

Main Methods:

• Site-directed mutagenesis of four conserved residues in E. coli RF1.
• Thermodynamic and kinetic analysis of RF1 mutants.
• Assessing RF1 binding affinity to the ribosome.
• Measuring the rate of peptide release.

Main Results:

• Mutations in RF1 significantly inhibited the binding of RF1 to the ribosome.
• Despite impaired ribosome binding, the mutations did not alter the rate of peptide release.
• Imperfect stop codon recognition did not prevent proper RF1 positioning on the ribosome.

Conclusions:

• The studied conserved residues in RF1 are important for ribosome binding but not for discriminating stop codons.
• Stop codon recognition is not strictly coupled to the proper positioning of RF1 on the ribosome for peptide release.
• These findings challenge the established model of coupled stop codon recognition and peptide release during translation termination.