| Symbol: | XPG_I |
| XPG_I | |
| Pfam: | PF00867 |
| Pfam Clan: | CL0464 |
| Interpro: | IPR006086 |
| Prosite: | PDOC00658 |
| Scop: | 1a77 |
| Cdd: | cd09868 |
In molecular biology, the XPG-I is a protein domain found on Xeroderma Pigmentosum Complementation Group G (XPG) protein.[1] The XPG protein is an endonuclease which repairs DNA damage caused by ultraviolet light (UV light). The XPG protein repairs DNA by a process called, Nucleotide excision repair. Mutations in the protein commonly cause Xeroderma Pigmentosum which often lead to skin cancer.
The function of the internal XPG (XPG-I) domain contains many of cysteine and glutamate amino acid residues that are frequently found in various enzyme active sites, DNA nucleases. The I domain, together with the N-terminal forms the catalytic domain that contains the active site.[2]
XPG cleaves the 5'-overhanging flap structure that is generated when DNA polymerase encounters the 5'-end of a downstream Okazaki fragment. It has both 5'endo-/exonuclease and 5'-pseudo-Y-endonuclease activities. Cleaves the junction between single and double-stranded regions of flap DNA. The endonuclease binds 2 magnesium ions per subunit, which probably participate in the reaction catalyzed by the enzyme. May bind an additional third magnesium ion after substrate binding.