Position of the Initiator and Peptidyl Sites in the E. coli Ribosome

If an initiation complex is formed with E. coli ribosomes, viral messenger RNA and formylmethionyl-tRNA and the unprotected messenger RNA is then digested with ribonuclease, the ribosome is still able to synthesize a pentapeptide fragment. The point of entry for messenger RNA on the ribosome therefore seems to be four codons removed from the initiator site. The same distance was found for the peptidyl site.