Purine bases at position 37 of tRNA stabilize codon-anticodon interaction in the ribosomal A site by stacking and Mg2+-dependent interactions.

The anticodon loop of tRNA contains a number of conserved or semiconserved nucleotides. In most tRNAs, a highly modified purine is found at position 37 immediately 3' to the anticodon. Here, we examined the role of the base at position 37 for tRNA(Phe) binding to the A site of Escherichia coli ribosomes.