Poly(A) polymerase (EC:2.7.7.19) catalyses template-independent extension of the 3'-end of a DNA or RNA strand by one nucleotide at a time. The Poxvirus enzyme creates the 3'(poly)A tail of mRNAs, and is a heterodimer of a catalytic and a regulatory subunit.

VP55 comprises three domains: the N-terminal or N domain, the central or catalytic domain, and the C-terminal or C domain, all three domains having distinct topologies. The N domain has an all alpha topology, with six of the eight helices forming three helix-hairpin-helix (HhH) motifs that are packed to create an elongated ensemble.

This superfamily entry includes the domain found at the N-terminus of the pox virus Poly(A) polymerase protein PMID:16678106.

INTERPRO:IPR024398, PFAM:PF12630,DOI:10.1016/j.molcel.2006.03.015