InterPro domain: IPR007012

In eukaryotes, polyadenylation of pre-mRNA plays an essential role in the initiation step of protein synthesis, as well as in the export and stability of mRNAs. Poly(A) polymerase, the enzyme at the heart of the polyadenylation machinery, is a template-independent RNA polymerase which specifically incorporates ATP at the 3' end of mRNA. The crystal structure of bovine poly(A) polymerase bound to an ATP analog at 2.5 A resolutio has been determined [ 1 ]. The structure revealed expected and unexpected similarities to other proteins. As expected, the catalytic domain of poly(A) polymerase shares substantial structural homology with other nucleotidyl transferases such as DNA polymerase beta and kanamycin transferase.

The central domain of Poly(A) polymerase shares structural similarity with the allosteric activity domain of ribonucleotide reductase R1, which comprises a four-helix bundle and a three-stranded mixed beta-sheet. Even though the two enzymes bind ATP, the ATP-recognition motifs are different.

1. Crystal structure of mammalian poly(A) polymerase in complex with an analog of ATP. EMBO J. 19, 4193-203