of C.zeylanoides, the anticodon loop distorted by G33 decreases the affinity toward LeuRS, judging from the Several lines of experiment have suggested that U33 is involved in the tRNA function on ribosomes, such as in observation that G33 increased the K m value for leucylation approximately 4-to 5-fold in comparison with that with rigid codon-anticodon interaction, proper GTP hydrolysis of the ternary complex and the efficient translation of prymidine bases at the position ( Figure 6B ). In C.cylindracea, m 1 G is replaced by A, which means that the tRNA termination codons (Bare et al., 1983; Dix et al., 1986) . Indeed, the replacement of G33 by U in C.cylindracea has lost the two major determinants for LeuRS, m 1 G and the discriminator base ( Figure 6C ). Consequently, LeuRS tRNA Ser CAG increased the efficiency of in vitro translation by 2-to 3-fold (data not shown). The negative effect of is unable to recognize tRNA Ser CAG at all, and G33 concomitantly loses its function as a modulator. LeuRS G33 on translation may indicate involvement in some mechanism for decoding the polysemous codon. This is, of course, unable to recognize other serine isoacceptor tRNAs corresponding to universal codons, because they possibility needs to be clarified by further study. Nevertheless, we have shown here that one of the roles of G33 is have modified A at position 37. How did this interaction between LeuRS and the suppression of leucylation, and we consider that the nucleotide at position 33 is not directly involved in tRNA Ser CAG evolve? Candida species utilizing CUG as serine can be classified into two distinct groups: group 1 recognition by LeuRS. On the basis of our observation that no leucylation was detectable in the C.cylindracea contains the species that have tRNA Ser CAG with leucylation activity, and includes C.zeylanoides, C.maltosa and tRNA Ser CAG variants in which G33 was replaced by a pyrimidine base (c-G33U and c-G33C), we speculate that others (see Figure 6B ); group 2, which is represented solely by C.cylindracea, contains species that have tRNA Ser CAG G33 influences the location and/or conformation of m 1 G37, accompanied by the alteration of the anticodon loop without leucylation activity ( Figure 6C ). A plausible evolutionary process is that group 1 would have arisen structure, decreasing the affinity of LeuRS toward tRNA Ser CAG.