The nucleotide sequence of phenylalanine tRNA of Xenopus laevis

The nucleotide sequence of Xenopus laevis phenylalanine tRNA extracted from oocytes was determined to be: pGCCGAAAUAm2GCUCm1AG DDGGGAGAGCm22 G psi psi AGACmUGmAAYA psi C UAAAGm7GDCm5CCUGGT psi CGm1AUCCCGG GUUUCGGCACCAoH. This result was achieved by analysing, with classical procedures [6], the oligonucleotides obtained after digestion by T1 or pancreatic ribonuclease. This sequence is identical to the mammalian sequence. It has been entirely conserved during 10(8) years, the time lapse between the divergence of amphibians and mammals in evolution. In contrast to 5S RNA, no important heterogeneity has been found in the oocyte sequence, suggesting that there is only a single sequence for tRNAphe in X. laevis. Small differences are seen in the elution pattern from RPC-5 columns for immature oocyte and somatic tRNAphe. They are probably due to a submodification of methyl-5-cytidine residues, which appear to be about half methylated in tRNAphe as well as in total tRNA from immature oocytes.