Initiator Protein Dependent Binding of Messenger RNA to the Ribosome

Translation of a genetic message starts by the attachment of the ribosome to the template RNA in a position corresponding to the beginning of the cistron to be translated into protein. Signals exist on messenger RNA (mRNA) which determine the site at which synthesis of the protein chain is initiated and the codewords AUG and GUG which correspond to the initiator N-formyl-methionyl-transfer RNA (F-met-tRNA) species (Clark and Marcker, 1966; Adams and Capecchi, 1966), must most probably be part of this signal. However, owing to the fact that methionine codons also occur internally in the cistron, at positions which do not mean initiation, one must assume that the signal indicating the beginning of a cistron must be more complex than just the methionine codon. Fidelity in the translation of mRNA will depend very much on the correct recognition by the ribosome of the initiation signal and the search for the mechanism...