Puromycin Analogues. Effect of Aryl-Substituted Puromycin Analogues on the Ribosomal Peptidyltransferase Reaction

A series of ortho- and para-substituted L-phenylalanylpuromycin analogues were synthesized and evaluated as substrates for the peptidyltransferase reaction of Escherichia coli ribosomes. Kinetic results reveal that substitution of the p-methoxy group of the puromycin molecule alters the peptidyltransferase activity of the molecule with the following decreasing order of substrate efficiencies: p-NH₂ > p-NHCOCH₃ > p-NO₂ = p-NHCO(CH₂)₂CH₃ > p-NHCOCH₂Br. However, the inability of the ribosome to tolerate a nitro group at the ortho position of the phenylalanine ring precluded the use of the photosensitive puromycin analogue, 2-nitro-4-azidophenylalanylpuromycin aminonucleoside (7a), as a photoaffinity label for the peptidyltransferase site.