Identification of specific Rp-phosphate oxygens in the tRNA anticodon loop required for ribosomal P-site binding

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• Ribosomal binding of transfer RNA (tRNA) to the P-site involves both codon-anticodon recognition and identification of tRNA structural features by the ribosome.
• Understanding these structural elements is key to deciphering the mechanism of translation initiation and elongation.

Purpose of the Study:

• To identify specific structural elements within the tRNA anticodon loop essential for P-site binding.
• To elucidate the role of these elements in stabilizing tRNA-ribosome interactions and facilitating correct tRNA-mRNA complex formation.

Main Methods:

• Phosphorothioate substitution-interference approach to probe phosphate oxygen involvement in tRNA P-site binding.
• Stereochemical analysis using synthetic anticodon arm analogues with Rp- and Sp-phosphorothioates.
• N-ethyl-N-nitrosourea modification-interference experiments on natural tRNAs.
• Utilizing the crystal structure of tRNA(Phe) for structural interpretation.

Main Results:

• Identified specific nonbridging Rp-phosphate oxygens in the anticodon loop of Escherichia coli tRNA(Phe) critical for P-site binding.
• Stereospecificity of phosphate oxygen involvement was confirmed.
• Similar interference patterns observed for yeast tRNA(Phe) and E. coli tRNA(fMet) suggest conserved recognition mechanisms across different tRNAs.
• Modification-interference experiments corroborated the importance of these phosphates.

Conclusions:

• Specific Rp-phosphate oxygens in the tRNA anticodon loop are essential for P-site binding.
• These phosphates may stabilize the anticodon loop's 'U-turn' conformation or directly interact with the ribosome.
• These findings highlight a conserved mechanism for tRNA selection by the ribosome, involving both sequence and structural recognition.