InterPro domain: IPR022894

Oligoribonuclease (Orn) is a DEDDh-type DnaQ-like 3'-5' exoribonuclease that is responsible for degrading small oligoribonucleotides to mononucleotides. It contains three conserved sequence motifs termed ExoI, ExoII and ExoIII, with a specific Hx(4)D conserved pattern at ExoIII. These motifs are clustered around the active site and contain four conserved acidic residues that serve as ligands for the two metal ions required for catalysis. Orn is essential for Escherichia coli survival [ 1 ]. The human homologue, also called Sfn (small fragment nuclease), is able to hydrolyse short single-stranded RNA and DNA oligomers. It plays a role in cellular nucleotide recycling [ 2 , 3 ].

1. The crystal structure of XC847 from Xanthomonas campestris: a 3'-5' oligoribonuclease of DnaQ fold family with a novel opposingly shifted helix. Proteins 65, 1036-40
2. The human homolog of Escherichia coli Orn degrades small single-stranded RNA and DNA oligomers. J. Biol. Chem. 275, 25900-6
3. Oligoribonuclease is a common downstream target of lithium-induced pAp accumulation in Escherichia coli and human cells. Nucleic Acids Res. 34, 2364-73