19] Half-molecules from phenylalanine-specific tRNA's

Abstract

Publisher Summary This chapter describes the isolation of half-molecules from phenylalanine-specific tRNAs. The tRNAs contain next to the anticodon a still unknown nucleoside, which is called Y or Y w . A nucleoside similar to Y or Y w is found also in tRNA Phe rat , but not in tRNA Phe E.coli . By mild treatment with acid, the base moiety of this nucleoside can be excised from the tRNAs. The phosphodiester bond linking the ribose to the next nucleotide can be split in an amine-catalyzed reaction, thus producing half-molecules of the tRNAs. tRNA phe isolated by chromatography on benzoylated DEAE-cellulose is pure enough for the preparation of half-molecules. At low concentrations of inorganic salts, the excision reaction is slower than in the absence of salts. Acid-modified tRNA Phe yeast shows full acceptor activity with yeast synthetase preparations. In contrast to unmodified tRNA Phe , which is charged also by E.coli synthetase under certain conditions, modified tRNA Phe is not charged by E.coli synthetases.