Codon-anticodon recognition: The missing triplet hypothesis

Abstract

The purpose of this article is to determine whether the rules for codon-anticodon recognition can roughly be the same as for double-stranded RNA associations or if some special configuration which allows one and only one of the bases to wobble is necessary to account for the presence of inosine in a certain number of anticodons in yeast and the presumed absence of related anticodons. It is proposed that the recognition of triplets in a double helical configuration of the type which seems to occur in the ordered segments of transfer RNA is necessarily ambiguous because of the interactions between non-hydrogen-bonded bases on opposite strands (diagonal interactions of stacking). It is then deduced that the complex patterns of degeneracy in codon-anticodon recognition can occur in a situation which is less unsymmetrical with respect to the three positions of the codon-anticodon association than assumed by the wobble hypothesis, provided that some of the potential anticodons be absent in the cell. Our hypothesis makes predictions of this type: if in the anticodon for alanine in yeast (IGC), inosine is substituted by guanine, the resulting modified tRNA will be recognized, in addition to GCC, by GUC which is a codon for valine.