cd05402

Nucleotidyltransferase (NT) domain of poly(A) polymerases and terminal uridylyl transferases; Poly(A) polymerases (PAPs) catalyze mRNA poly(A) tail synthesis, and terminal uridylyl transferases (TUTases) uridylate RNA. PAPs in this subgroup include human PAP alpha, mouse testis-specific cytoplasmic PAP beta, human nuclear PAP gamma, Saccharomyces cerevisiae PAP1, TRF4 and-5, Schizosaccharomyces pombe caffeine-induced death proteins -1, and -14, Caenorhabditis elegans Germ Line Development-2, and Chlamydomonas reinhardtii MUT68. This family also includes human U6 snRNA-specific TUTase1, and Trypanosoma brucei 3'-TUTase-1,-2, and 4. This family belongs to the Pol beta-like NT superfamily. In the majority of enzymes in this superfamily, two carboxylates, Dx[D/E], together with a third more distal carboxylate, coordinate two divalent metal cations involved in a two-metal ion mechanism of nucleotide addition. For the majority of proteins in this family, these carboxylate residues are conserved.