Post-transcriptional RNA editing in Trypanosomatids (pathogenic protozoa) is catalyzed by a large multiprotein complex, the editosome. A key editosome enzyme, RNA editing terminal uridylyl transferase 2 (TUTase 2; RET2) catalyzes the uridylate addition reaction. RET2 structure consists of three domains: the N-terminal domain (NTD), the middle domain (MD) and the C-terminal domain (CTD). This MD domain is mainly composed of six helices and a four-stranded antiparallel beta-sheet. structural comparison reveals that the fold of this MD is topologically similar to the binding domains of several RNA-binding proteins such as the RNA-binding domain of the U1A spliceosomal protein, the RRM domain of the human La protein and the CTD of an archaeal CCA-adding enzyme. The CTD of the archaeal CCA-adding enzyme has been shown to bind double-stranded tRNA stem substrate through the alpha-helices regions. Hence it is suggested that this domain might be an RNA-binding domain [1].

1: Structural basis for UTP specificity of RNA editing TUTases from Trypanosoma brucei. Deng J, Ernst NL, Turley S, Stuart KD, Hol WG; EMBO J. 2005;24:4007-4017. PMID:16281058