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 | |||||||||
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![]() 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 | ||||||||
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Function
editThe 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
editXPG 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
edit- ^ 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.