Expression, purification, crystallization and preliminary X-ray diffraction crystallographic study of PurH from Escherichia coli

In bacteria and eukaryotes, the last two steps of de novo purine biosynthesis are catalyzed by bifunctional purine-biosynthesis protein (PurH), which is com­posed of two functionally independent domains linked by a flexible region. The N-terminal domain possesses IMP cyclohydrolase activity and the C-­terminal domain possesses aminoimidazole-4-carboxamide ribonucleotide transformyl­ase activity. This study reports the expression, purification, crystallization and preliminary X-ray crystallographic analysis of PurH from Escherichia coli with an N-terminal His₆ tag. The crystals diffracted to a maximum resolution of 3.05 Å and belonged to the monoclinic space group P2₁, with unit-cell parameters a = 76.37, b = 132.15, c = 82.64 Å, β = 111.86°.