DEDDy 3'-5' exonuclease domain of Ribonuclease D and similar proteins
Ribonuclease (RNase) D is a bacterial enzyme involved in the maturation of small stable RNAs and the 3' maturation of tRNA. It contains a DEDDy-type DnaQ-like 3'-5' exonuclease domain possessing three conserved sequence motifs termed ExoI, ExoII and ExoIII, with a specific YX(3)D 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. In vivo, RNase D only becomes essential upon removal of other ribonucleases. Eukaryotic RNase D homologs include yeast Rrp6p, human PM/Scl-100, and the Drosophila melanogaster egalitarian protein.