Primary structure of Escherichia coli tRNA UUR Leu. Presence of an unknown adenosine derivative in the first position of the anticodon which recognizes the UU codon series.

The primary structure of Escherichia coli tRNA UUR Le which recognizes the UU series of codons has been determined. The sequence is pG-C-C-C-G-G-A-s4U-G-G-U-G-G-A-A-D-C-Gm-C-D-A-G-A-C-A-C-A-A-G-G-G-A-psi-U-N-A-A-ms2i6A-A-psi-C-C-C-C-U-C-G-G-C-G-G-C-G-U-U-C-G-C-G-C-U-G-U-G-C-G-G-G-T-psi-C-A-A-G-U-C-C-C-G-C-U-C-C--G-G-G-U-A-C-C-A. The chain length of tRNA UUR Leu is 87 residues, the same as other E. coli tRNA Leu s and T4 phage-coded tRNA Leus. Its sequence is especially similar to that of E. coli tRNA2 Leu in the Darm and T psi C arm regions. E. coli tRNA UUR Leu contains an unknown modified nucleoside in the first position of the anticodon and was shown by mass spectrometry and chemical degradation to be an adenosine derivativee. Addition of tRNA UUR Leu to a cell-free protein-synthesizing system with high Mg2+ concentration resulted in the formation of polyleucine miscoded by poly(U), indicating that the unknown modified nucleoside exhibits a tendency to recognize U under certain conditions.