[Donor site of E. coli ribosomal peptidyltransferase].

The mechanism of 5'-cytidilic acid stimulation of the reaction between 2'(3')-O-formylmethionine ester of 5'-adenylic acid and phenylalanyl-tRNA catalyzed by E. coli ribosomes has been studied. It has been shown that cytidilic acid binds to the donor site of the peptidyltransferase in the area which is usually occupied by the second nucleotide residue of the peptidyl-tRNA 3'-end. After the binding cytidilic acid stimulates effectively the donor activity of formylmethionine ester of adenylic acid. A number of compounds have been tested as possible stimulants. Both the chemical nature of stimulant and its conformation are important for the stimulating action. A hypothetic scheme is suggested explaining possible causative factors of peptidyl-tRNA translocation from the acceptor site to the donor site after peptide bond formation.