A tRNA modification with aminovaleramide facilitates AUA decoding in protein synthesis

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Transfer RNAs (tRNAs) with modified anticodons are crucial for accurate mRNA translation.
• Bacterial tRNAs for isoleucine (tRNA^Ile) typically use a modified cytidine-lysidine (L) at anticodon position 34 to read the AUA codon.

Purpose of the Study:

• To identify and characterize novel tRNA modifications involved in AUA codon decoding.
• To investigate the evolutionary variation of essential tRNA modifications.

Main Methods:

• Cryo-electron microscopy for structural analysis of tRNA-codon interactions.
• Biochemical assays to assess tRNA charging and decoding capabilities.

Main Results:

• A new cytidine derivative, 2-aminovaleramididine (ava2C), was identified in tRNAs^Ile from plant organelles and some bacteria.
• ava2C at anticodon position 34, similar to L34, mediates both isoleucine charging and AUA codon recognition.
• Structural analysis revealed specific interactions between the ava2C terminal amide group and the mRNA residue adjacent to the AUA codon.

Conclusions:

• This study uncovers evolutionary diversity in essential tRNA modifications.
• The findings elucidate the molecular mechanism by which ava2C facilitates AUA codon decoding.