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

The primary nucleotide sequence of tRNA&, from Es&erichia co2i has been determined. The sequence of 76 nut cleotides is pG-C-U-G-A-U-A-U-A-G-C-U-C-A-G-D-D-G-GD-A-G~A~G-C~E~C-A~C~C~C-U-U~G-G~U~mt~A-A~G~G-GlUl GeA-G17mG-UIC-G-G-C-A-G-T -~-C-G-A-A-U-C-U-G-C-CU-A-U-C-A-G-C-A-C-C-A-OH, where Din positions 16, 17, and 20 is 5,64ihydrouridylic acid, mt6Aat position 37 is probably the 3’-phosphate of N-[(9-P-D-ribofuranosylpurin-6yI)-IV-methylcarbamoyllthreonine, m7Gat position 46 is 7methylguanylic acid, Tm at position 54 is ribothymidylic acid, and #at position SS is pseudouridylic acid, Comparisons of the sequence of tRNAz&,c with those of other E. coli tRNAs have revealed 72 % homology with tRNAz$&, 71% homology with tRNAy&, 67% homology with tRNA,Y”:,2p,, and 67 % homology with tRNAzcG& The possibility that these tRNAs are descendants of a common ancestral gene is discussed.