Crystallization of the xeroderma pigmentosum group F endonuclease from Aeropyrum pernix.

The xeroderma pigmentosa group F protein (XPF) is a founding member of a family of 3'-flap endonucleases that play an essential role in nucleotide-excision repair, DNA replication and recombination. The XPF gene has been cloned from Aeropyrum pernix, encoding a 254-residue protein (apXPF). Recombinant protein was produced in Escherichia coli and purified by three chromatographic steps. Three different crystal forms of apXPF were grown in trigonal, monoclinic and triclinic systems. The trigonal crystals diffracted to 2.8 A and were grown in the presence of double-stranded DNA. Monoclinic crystals were grown without DNA and diffracted to 3.2 A. Triclinic crystals were grown from a truncated apXPF protein lacking the tandem helix-hairpin-helix motifs and diffracted to 2.1 A.