| Abstract: | Nucleotide sequence analysis of one of several tRNA genes cloned from Tetrahymena thermophila macronuclear DNA indicated that it corresponds to a tRNA species having TTA as anticodon. Subsequently, the tRNA species corresponding to that gene was isolated and its nucleotide sequence was determined by post-labeling techniques. The nucleotide sequence was found to be pG-G-U-U-C-C-A-U-A-m2G-U-A-psi-A-G-D-G-G-D- D-A-G-U-A-C-U-G-G-G-G-A-Cm-U-Um-U-A-i6A-A-psi-C-C-C-U-U-G-A-C- m5C-U-G-G-G-U-psi-C-G-m1A-A-U-C-C-C-A-G-U-G-G-G-A-C-C-U-C-C-AOH. This tRNA sequence exactly matched the DNA sequence of the corresponding tRNA gene. The first position of anticodon is 2'-O-methyluridine (Um), forming UmUA as the anticodon, which presumably recognizes the ochre termination codon UAA. This tRNA species is aminoacylated with glutamine by a Tetrahymena crude aminoacyl tRNA synthetase fraction, suggesting that ochre termination codon is used as a glutamine codon during cytoplasmic protein synthesis in Tetrahymena. |
