Exonuclease that cleaves single-stranded 3' overhangs of double-stranded RNA. Has no activity with 5' overhangs. Has negligible endonuclease activity. Can bind ATP, dATP and AMP (in vitro); the nucleotide occupies the predicted substrate binding site. Binds 1 Mg(2+) ion per subunit. Inhibited by EDTA. Homodimer. Member of the DEDD group of RNAses that are characterized by the presence of four acidic residues in the active site. These residues are conserved even when the proteins have highly divergent sequences. Has high structural similarity to RNase T despite very low sequence identity.