<p>This entry represents a beta-barrel domain consisting of a duplication of a beta/alpha/beta/alpha/beta motif, which is found in the 2'-5' RNA ligase LigT [<cite idref="PUB00017746"/>], the tRNA splicing product Appr>p cyclic nucleotide phosphodiesterase [<cite idref="PUB00013260"/>], and as the catalytic domain in 2',3'-cyclic nucleotide 3'-phosphodiesterase [<cite idref="PUB00036006"/>]. This beta-barrel domain is similar in structure to the beta-barrel found in prokaryotic DNA topoisomerases I and III. </p><p>The 2'-5' RNA ligase family members are bacterial and archaeal RNA ligases that ligate 5' and 3' half-tRNA molecules with 2',3'-cyclic phosphate and 5'-hydroxyl termini, respectively, to the product containing the 2'-5' phosphodiester linkage.</p><p>Appr>p cyclic nucleotide phosphodiesterase (CPDase) from <taxon tax_id="3702">Arabidopsis thaliana</taxon> (Mouse-ear cress) is an enzyme involved in the tRNA splicing pathway. CPDase acts to hydrolyse the tRNA splicing product ADP-ribose 1",2"-cyclic phosphate (Appr>p) to the monoester ADP-ribose 1"-phosphate (Appr-1"p). 2',3'-cyclic uridine vanadate is a putative inhibitor of CPDase. The crystal structure of CPDase reveals a bilobal arrangement of duplicated beta-alpha-beta-alpha-beta motifs, where the antiparallel beta sheet forms a barrel similar to that of prokaryotic DNA topoisomerases I and III [<cite idref="PUB00007407"/>]. CPDase contains six cysteine residues, four of which form two intramolecular disulphide bridges [<cite idref="PUB00013260"/>].</p>