Purification and properties of the major tRNAHis from sheep liver

The major isoacceptor of tRNAHis from sheep liver was purified. Two different methods were described which both took advantage of the presence of the hypermodified Q nucleotide in this tRNA. In the first procedure, CNBr treatment of tRNA which was previously enriched in tRNAHis greatly increased the efficiency of the subsequent chromatographic steps. The tRNAHis obtained by this technique showed a specific activity of 1,690 picomoles of histidine per A260 unit. In the second one, a twenty-fold enrichment in tRNAHis was obtained by fractionation of crude tRNA on acetylated DBAE-cellulose columns. The nucleotide composition of the tRNA obtained by the CNBr procedure was determined. No thymine ribotide could be detected. When this tRNA was submitted to periodate oxidation and tritium borohydride reduction, a radioactive label was introduced in this molecule which was assumed to be located in the Q nucleotide.