XPG I protein domain
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.
| XPG_I | |||||||||
|---|---|---|---|---|---|---|---|---|---|
 flap endonuclease-1 from methanococcus jannaschii | |||||||||
| Identifiers | |||||||||
| Symbol | XPG_I | ||||||||
| Pfam | PF00867 | ||||||||
| Pfam clan | CL0464 | ||||||||
| InterPro | IPR006086 | ||||||||
| PROSITE | PDOC00658 | ||||||||
| SCOP2 | 1a77 / SCOPe / SUPFAM | ||||||||
| CDD | cd09868 | ||||||||
| |||||||||
Function
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]
Mechanism
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.
References
- O'Donovan A, Scherly D, Clarkson SG, Wood RD (1994). "Isolation of active recombinant XPG protein, a human DNA repair endonuclease". J Biol Chem. 269 (23): 15965–8. doi:10.1016/S0021-9258(17)33956-X. PMID 8206890.
- Clarkson SG (2003). "The XPG story". Biochimie. 85 (11): 1113–21. doi:10.1016/j.biochi.2003.10.014. PMID 14726017.