Separation of isoacceptor cysteine transfer ribonucleic acids of bakers' yeasts.

Isoacceptor species of certain amino acid-specific transfer ribonucleic acids (tRNAs) were fractionated by gel permeation chromatography using Sephadex G-100. The separation is attributed to the 20% ethanol-1% NaCl solvent and to the characteristics of Sephadex. Isoacceptor tRNAs specific for cysteine, arginine, phenylalanine, and histidine were recovered from commercial tRNA of yeast by this method.

Mechanism for the incorporation of S-(1,2,3,4-tetrahydro-2-hydroxy-1-naphthyl)-L-cysteine into protein.

Evidence is presented which indicates that S-(1,2,3,4-tetrahydro-2-hydroxy-1-naphthyl)-L-cysteine (THN-cysteine), formed by the reaction of 1,2-epoxy-THN with cysteine, can be incorporated into protein; The position of incorporation of THN-cysteine into protein would depend on whether the epoxide of THN reacts with cysteinyl-tRNACyS or with cysteine. In both cases, the mechanism of incorporation of THN-cysteine into protein is the same as for the natural amino acids. For example, the incorporation of THN-cysteinyl-tRNACyS is stimulated by Poly-UG, the code for tRNACyS, and would be expected to be substituted for cysteine in protein being synthesized, whereas THN-cysteine not previously esterified to tRNA is activated by the isoleucyl- and valyl-RNA synthetases, and its incorporation is stimulated by Poly-AU and Poly-UG, respectively.