An adenosine deaminase that generates inosine at the wobble position of tRNAs

Several transfer RNAs (tRNAs) contain inosine (I) at the first. position of their anticodon (position 34): this modification is thought. to enlarge th e codon recognition capacity during protein synthesis. The tRNA-specific ad enosine deaminase of Saccharomyces cerevisiae that forms I-34 in tRNAs is d escribed. The heteroclimeric enzyme consists of two sequence-related subuni ts (Tad2p/ADAT2 and Tad3p/ADAT3), both of which contain cytidine deaminase (CDA) motifs. Each subunit is encoded by an essential gene (TAD2 and TAD3), indicating that I-34 is an indispensable base modification in elongating t RNAs. These results provide an evolutionary Link between the CDA superfamil y and RNA-dependent adenosine deaminases (ADARs/ADATs).