lsomeric Phenylalanyl-tRNAs. Position of the Aminoacyl Moiety During Protein Biosynthesis
Abstract
The preparation of phenylalanyl-tRNA terminating in 3′-deoxyadenosine has been achieved by incubation of abbreviated tRNA (tRNA-CpCOH) with 3′-deoxyadenosine 5′-diphosphate and polynucleotide phosphorylase (EC 2.7.7.8), followed by aminoacylation. The isomeric phenylalanyl-tRNA terminating in 2′-deoxyadenosine was constructed by incubation of tRNA-CpCOH with 2′-deoxy-3′-O-phenylalanyladenosine 5′-diphosphate and polynucleotide phosphorylase. While tRNA is aminoacylated at the 2′-position, only the 3′-aminoacyl-tRNA is active as a peptide acceptor in the peptidyltransferase reaction. Both modified tRNAs were bound to the A-site as efficiently as unmodified tRNA, but neither was so efficient at P-site binding or as an acceptor in the peptidyltransferase reaction. Neither of the modified tRNAs acted as a donor in the peptidyltransferase reaction.
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