ISOLATION OF YEAST TYROSINE AND TRYPTOPHAN TRANSFER RIBONUCLEIC ACIDS

Uncharged yeast (Saccharomyces cerevisiae) transfer ribonucleic acids (tRNAs) may be entirely eluted from a column of benzoylated DEAE-cellulose (BD-cellulose) by 1 M NaCl, with the sole exception of phenylalanine transfer ribonucleic acid (tRNAPhe). Tyrosine ribonucleic acid (tRNATyr) and tryptophan ribonucleic acid (tRNATrp) when charged with their respective amino acids bind strongly to BD-cellulose. Tyrosyl-tRNATyr is not eluted by NaCl alone at concentrations up to 1 M but may be eluted with 1 M NaCl containing a small proportion of ethanol. Tryptophanyl-tRNATrp, although partly eluted by NaCl at concentrations greater than 0.8 M, requires the presence of ethanol for complete elution. These properties of the aminoacyl-tRNAs were utilized to obtain highly purified preparations of tRNATyr and tRNATrp in three simple Chromatographic steps, each step using a column of BD-cellulose. First, tRNAphe was removed together with some nontransfer ribonucleic acid material. Secondly, the remaining mixture of tRNAs was charged with either tyrosine or tryptophan and the charged species were isolated. Finally, the charged tRNA was stripped of amino acid and rechromatographed to obtain further purification. The final preparations accepted 1.86 and 1.93 nmoles of tyrosine or tryptophan, respectively, per A260 unit, corresponding to purification factors of approximately 32 and 28. It was estimated that both preparations were more than 94 % pure. © 1968, American Chemical Society. All rights reserved.