Aprataxin is a DNA-binding protein that catalyses (among other activities) the 5′ decapping of Gpp-DNA (formed by homologs of RtcB3 from the bacterium?Myxococcus xanthus). The enzyme binds the guanylate group to a histidine residue at its active site, forming a covalent enzyme-nucleotide phosphate intermediate, followed by the hydrolysis of the guanylate from the nucleic acid and eventual release. The enzyme forms a 5′-phospho terminus that can be efficiently joined by “classical” ligases. The enzyme also possesses the activity of EC?3.1.11.7, DNA-(5′-diphosphoadenosine) diphosphatase and EC?3.1.12.2, DNA-3′-diphospho-5′-guanosine diphosphatase.
![Example Structure of guanosine-5'-diphospho-5'-[DNA] diphosphatase EC#: 3.1.11.8](/wp-content/uploads/enzyme-structure/3.1.11.8.jpg)