Members of this family are bacterial and archaeal RNA ligases that are able to ligate tRNA half molecules containing 2',3'-cyclic phosphate and 5' hydroxyl termini to products containing the 2',5' phosphodiester linkage. Each member of this family contains an internal duplication, each of which contains an HXTX motif that defines the family. The structure of a related protein is known [1]. They belong to the 2H phosphoesterase superfamily [2]. They share a common active site, characterised by two conserved histidines, with vertebrate myelin-associated 2',3' phosphodiesterases, plant Arabidopsis thaliana CPDases and several several bacteria and virus proteins.

1: Structure and mechanism of activity of the cyclic phosphodiesterase of Appr>p, a product of the tRNA splicing reaction. Hofmann A, Zdanov A, Genschik P, Ruvinov S, Filipowicz W, Wlodawer A; EMBO J 2000;19:6207-6217. PMID:11080166

2: Detection of novel members, structure-function analysis and evolutionary classification of the 2H phosphoesterase superfamily. Mazumder R, Iyer LM, Vasudevan S, Aravind L; Nucleic Acids Res 2002;30:5229-5243. PMID:12466548