User:Cboursnell/Sandbox/Z/2 5 RNA ligase

This entry represents a domain found in a number of known and predicted phosphoesterases. These include bacterial and archaeal 2',5' RNA ligases, and a family of predicted phosphoesterases known as the YjcG family. The 2',5' RNA ligases perform a reversible, ATP-independent 2'-5'-ligation of what is presumably a non-phyiological substrate: half-tRNA splice intermediates from an intron-containing yeast tRNA. The physiological substrate(s) in prokaryotes may include small 2',5'-link-containing oligonucleotides, perhaps with regulatory or biosynthetic roles. This domain contains a conserved HXTX motif which is thought to be important for catalytic activity, as it is in the related enzyme cyclic nucleotide phosphodiesterase (CPDase). In 2',5' RNA ligase this domain is duplicated, with the two conserved motifs forming the proposed active site, which is analogous to that of CPDase.