Structural basis of tRNA recognition by the widespread OB fold

Area of Science:

• Structural biology
• Molecular biology
• Biochemistry

Background:

• The oligonucleotide/oligosaccharide-binding (OB)-fold is a versatile protein domain involved in various cellular processes, including nucleic acid and protein recognition.
• OB-fold proteins like bacterial Trbp and yeast Arc1p are implicated in transfer RNA (tRNA) metabolism, but their precise binding mechanisms remain unclear.

Purpose of the Study:

• To elucidate the structural basis of tRNA recognition by the OB-fold protein Trbp from Aquifex aeolicus.
• To investigate the molecular interactions between Trbp and tRNA at the 3' end.

Main Methods:

• X-ray crystallography to determine the co-crystal structure of Trbp111 bound to tRNA^Ile at 2.6 Å resolution.
• Site-directed mutagenesis and biophysical assays to validate the identified interactions.

Main Results:

• The co-crystal structure reveals that Trbp recognizes tRNA exclusively through its 3' end, specifically the single-stranded 3' CA dinucleotide.
• The OB-fold precisely interacts with the terminal CA sequence and its single-stranded conformation, a universal feature of mature tRNAs.
• Yeast Arc1p utilizes additional interactions with the tRNA body beyond the 3' end.

Conclusions:

• This study uncovers a previously unrecognized mode of tRNA recognition mediated by the OB-fold, focusing on the 3' terminal CA dinucleotide.
• The findings provide novel insights into protein-tRNA interactions relevant to tRNA aminoacylation, folding, localization, trafficking, and potential piracy.