The Nucleotide Sequence of a Threonine Transfer Ribonucleic Acid from Escherichia coli

The primary nucleotide sequence of tRNAThracu/c from Escherichia coli has been determined. The sequence of 76 nucleotides is pG-C-U-G-A-U-A-U-A-G-C-U-C-A-G-D-D-G-G-D-A-G-A-G-C-E-C-A-C-C-C-U-U-G-G-U-mt6A-A-G-G-G-U-G-A-G-7mG-U-C-G-G-C-A-G-T-ψ-C-G-A-A-U-C-U-G-C-C-U-A-U-C-A-G-C-A-C-C-A-OH, where D-in positions 16, 17, and 20 is 5,6-dihydrouridylic acid, mt6A-at position 37 is probably the 3'-phosphate of N-[(9-β-d-ribofuranosylpurin-6-yl)-N-methylcarbamoyllthreonine, m7G-at position 46 is 7-methylguanylic acid, T-at position 54 is ribothymidylic acid, and ψ-at position 55 is pseudouridylic acid. Comparisons of the sequence of tRNAThracu/c with those of other E. coli tRNAs have revealed 72% homology with tRNAGly 3ggu/c, 71% homology with tRNAIleaau/c, 67% homology with tRNAVal 2Aguu/c, and 67 % homology with tRNAVal 2Bguu/c. The possibility that these tRNAs are descendants of a common ancestral gene is discussed.