ARGININE AMINOACYLATION IDENTITY IS CONTEXT-DEPENDENT AND ENSURED BY ALTERNATE RECOGNITION SETS IN THE ANTICODON LOOP OF ACCEPTING TRANSFER-RNA TRANSCRIPTS

Yeast arginyl-tRNA synthetase recognizes the nonmodified wild-type tra nscripts derived from both yeast tRNA(Arg) and tRNA(Asp) with equal ef ficiency, It discriminates its cognate natural substrate, tRNA(Arg), f rom non-cognate tRNA(Asp) by a negative discrimination mechanism where by a single methyl group acts as an anti-determinant. Considering thes e facts, recognition elements responsible for specific arginylation in yeast have been searched by studying the in vitro arginylation proper ties of a series of transcripts derived from yeast tRNA(Asp), consider ed as an arginine isoacceptor tRNA, In parallel, experiments on simila r tRNA(Arg) transcripts were performed, Unexpectedly, in the tRNA(Arg) context, arginylation is basically linked to the presence of residue C35, whereas in the tRNA(Asp) contest, it is deeply related to that of C36 and G37 but is insensitive to the nucleotide at position 35, Each of these nucleotides present in one host, is absent in the other host tRNA, Thus, arginine identity is dependent on two different specific recognition sets according to the tRNA framework investigated.