Movement of tRNA but not the nascent peptide during peptide bond formation on ribosomes.

The results from experiments involving nonradiative energy transfer indicate that a fluorescent probe on the 5'-end of tRNA(Phe) moves more than 20 A towards probes on ribosomal protein L1 as a peptide bond is formed during the peptidyl transferase reaction on Escherichia coli ribosomes. The peptide itself moves no more than a few angstroms during peptide bond formation, as judged by the movement of fluorescent probes attached to the phenylalanine amino group of phenylalanyl-tRNA. Other results demonstrate that an analogue of peptidyl-tRNA, deacylated tRNA, and puromycin can be bound simultaneously to the same ribosome, indicating that there are three physically distinct sites to which tRNA is bound during the reaction steps by which peptides are elongated. The results appear to be consistent with the displacement model of peptide elongation.