Crick et al. (1961) were the first to demonstrate experimentally that the genetic code is made up of triplets. Since then the functions of all 64 of the possible triplets have been confirmed by the concerted efforts of many laboratories (1966 Cold Spring Harbor Symposium, entire volume). Implicit in a great deal of this research was the assumption that the translation apparatus reads messenger RNA (mRNA) one codon at a time and that its response to a particular codon, read in phase, should be the same regardless of the surrounding nucleotide sequence. Still, there is increasing evidence that in at least one case, initiation, the translation apparatus does respond to a nucleotide sequence larger than a single codon. For instance, GUG is recognized by N-formyl-methionyl tRNA (F-met-tRNA) when it initiates a chain and by valyl-tRNA when it occurs in the middle of a protein. Similarly, AUG can be recognized by...
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Salser et al. (1969) studied this question.