Studies on tRNA Nucleotidyltransferase from Baker's Yeast

Under special conditions, tRNA nucleotidyltransferase is able to add unusual terminal sequences to yeast tRNAPhe whose CCA end has been sequentially removed. By incubating tRNA‐XCCPhe, tRNA‐XCPhe or tRNA‐XPhe with ATP alone, the following tRNAPhe species are obtained: tRNA‐XCCAPhe (normal sequence), tRNA‐XCAPhe and tRNA‐XAPhe When the degraded tRNAs are incubated with CTP alone, in all cases the sequence tRNA‐XCCCPhe is synthesized, which is able to accept one AMP, thus leading to tRNA‐XCCCAPhe. This compound can be aminoacylated by phenylalanyl‐tRNA synthetase, in contrast to tRNA‐XCAPhe and to tRNA‐XAPhe.