Polyribonucleotide nucleotidyltransferase (PNPase) is a member of the RNase_PH family, named after the bacterial Ribonuclease PH, a 3'-5' exoribonuclease. Structurally, all members of this family form hexameric rings. In the case of PNPase the complex is a trimer, since each monomer contains two tandem copies of the domain. PNPase is involved in mRNA degradation in a 3'-5' direction and in quality control of ribosomal RNA precursors. It is part of the RNA degradosome complex and binds to the scaffolding domain of the endoribonuclease RNase E.
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