SUBSTRATE SPECIFICITY OF RIBOSOMAL PEPTIDYL TRANSFERASE - 2'(3')-O-AMINOACYL NUCLEOSIDES AS ACCEPTORS OF PEPTIDE CHAIN ON AMINO ACID SITE

Synthetic substrates were used to investigate the specificity of the acceptor site of ribosomal peptidyl transferase. The results may be summarized as follows: 1. (i) Simple synthetic compounds, namely 2′(3′)-O-aminoacyl-adenosines representing the ultimate terminal residue of aminoacyl-tRNA, can replace aminoacyl-tRNA in the transfer reaction and serve as acceptors of the nascent peptide residue, both with AcPhe-tRNA‡ ‡ Abbreviations used: AcPhe, l-acetylphenylalanine; AcPhePhe, l-acetylphenylalanyl-l-phenylalanine; AcPhe-puromycin, l-acetylphenylalanyl-puromycin; A-Gly, 2′(3′)-O-glycyl-adenosine; pA-Gly, 2′(3′)-O-glycyladenosine-5′-monophosphate; CpA-Gly, cytidylyl (3′ → 5′)-2′(3′)-O-glycyladenosine; A > (CH2NH2).(OEt), 2′,3′-O-aminomethyl-ethoxymethylenadenosine; A-Phe, 2′(3′)-O-l-phenylalanyladenosine; A-PhePheAc, 2′(3')-O-l-acetylphenylalanyl-l-phenyl-alanyladenosine; dA-Phe, 3′-O-l-phenylalanyl-2′-deoxyadenosine; C-Phe, 2′(3′)-O-l-phenylalanylcytidine; C-PhePheAc, 2′(3′)-O-l-acetylphenylalanyl-l-phenylalanylcytidine; G-Phe, 2′(3′)-O-l-phenylalanylguanosine; I-Phe, 2′(3′)-O-l-phenylalanylinosine; I-PhePheAc, 2′(3′)-O-l-acetylphenylalanyl-l-phenylalanylinosine; U-Phe, 2′(3′)-O-l-phenylalanyluridine; AcPhe-tRNA, l-acetylphenylalanyl-tRNA; (Lys)n-tRNA, l-oligolysyl-tRNA. and with (Lys)n-tRNA as the peptide donor. 2. (ii) The acceptor activity of the substrates is influenced by the nature of the side chain of the amino acid residue bound to adenosine; A-Phe was nearly as active as puromycin while A-Gly and A > (CH2NH2). (OEt) were inactive. 3. (iii) For an association between ribosomal peptidyl-transferase and the acceptor substrates the presence of free 2′-OH group in the ribose moiety of aminoacyl-adenosines is required as is shown by the low activity of dA-Phe in comparison with A-Phe. 4. (iv) The acceptor activity of the substrates tested is specific with respect to the nucleoside to which the amino acid residue is bound. Activity decreased in the sequence puromycin, A-Phe, I-Phe, C-Phe; G-Phe and U-Phe did not serve as acceptors of the peptide chain. Using AcPhe-tRNA as the donor of the AcPhe residue and A-Phe, C-Phe and I-Phe as acceptors, we isolated A-PhePheAc, C-PhePheAc and I-PhePheAc as terminal products of the reaction. The individual building blocks of aminoacylribonucleosides tested as such did not act as acceptors. Negative results were obtained with ammonium ions, tyramine, free amino acids, their amides and esters, adenosine, inosine and the puromycin aminonucleoside. © 1969.