<p>Prokaryotic ribonuclease PH (<db_xref db="EC" dbkey="2.7.7.56"/>) (RNase PH) is a phosphorolytic exoribonuclease that removes nucleotide residues following the -CCA terminus of tRNA and adds nucleotides to the ends of RNA molecules by using nucleoside diphosphates as substrates [<cite idref="PUB00002736"/>]. There is a similar protein in <taxon tax_id="6239">Caenorhabditis elegans</taxon> that belongs to this group.</p><p>More information about these proteins can be found at Protein of the Month: RNA Exosomes [<cite idref="PUB00035573"/>]. This entry represents a highly conserved region which is located in the central part of these proteins.</p>