A novel reaction of reticulocyte peptide-chain elongation factor, EF2, with guanosine nucleotides

The formation of phenylalanyl puromycin from phenylalanyl-tRNA, bound nonenzymically or enzymically to reticulocyte ribosomes, requires the peptide-chain elongation factor, EF2², and GTP. However the GTP analogue, GDPCP, may replace GTP to a significant extent in this reaction. Other purine or pyrimidine nucleotides have little or no activity. Multistep experiments with either GTP or GDPCP indicate that binding of EF2 to the ribosome for subsequent peptide formation may be a portion of the activity of the EF2 (independent of the translocation reaction) during the elongation process. Neomycin inhibits the formation of phenylalanyl puromycin using either GTP or GDPCP in this system.