Expression, purification, crystallization and preliminary X-ray analysis of Escherichia coli argininosuccinate synthetase

A recombinant form of Escherichia coli argininosuccinate synthetase with a C-terminal polyhistidine affinity tag has been expressed, purified and subsequently crystallized using the hanging-drop vapour-diffusion technique. The crystals grow as large rectangular chunks with unit-cell dimensions a = 79.70, b = 105.84, c = 127.33 Å, α = β = γ = 90°. The crystals exhibit the symmetry of space group I 222 and diffract to a minimum d -spacing of 1.6 Å at station X8C of the National Synchrotron Light Source, Brookhaven National Laboratory. On the basis of density calculations, one monomer of this homotetrameric protein is predicted per asymmetric unit (Matthews coefficient V m = 2.69 Å 3 Da −1 ).