Modified Nucleosides in the First Positions of the Anticodons of tRNA and tRNA from Escherichia coli

Minor leucine tRNA species, tRNA and tRNA , from Escherichia coli B have been reported to recognize leucine codons UUA and UUG [Goldman, E., Holmes, W. M., and Hatfield, G. W. (1979) J. Mol. Biol. 129, 567−585]. In the present study, these two tRNALeu species were purified from E. coli A19, and the nucleotide sequences were determined by a post-labeling method. tRNA was found to correspond to the tRNA gene reported as su°6 tRNA [Yoshimura, M., Inokuchi, H., and Ozeki, H. (1984) J. Mol. Biol. 177, 627−644]. The first letter of the anticodon was identified to be 2‘-O-methylcytidine (Cm). tRNA was identified as the minor leucine tRNA that has been sequenced previously (tRNA ) [Yamaizumi, Z., Kuchino, Y., Harada, F., Nishimura, S., and McCloskey, J. A. (1980) J. Biol. Chem. 255, 2220−2225]. There was an unidentified modified nucleoside (N*) in the first position of the anticodon of tRNA . Nucleoside N* was isolated to homogeneity (1 A260 unit). By 1H NMR spectroscopy, nucleoside N* was found to be a 2‘-O-meth...