Expression, purification, crystallization and preliminary x-ray analysis of escherichia coli 5′-methylthioadenosine/S-adenosylhomocysteine nucleosidase

A recombinant form of Escherichia coli 5'-methylthioadenosine/ S-adenosylhomocysteine nucleosidase (E.C. 3.2.2.9) has been purified to homogeneity and crystallized using the hanging-drop vapour-diffusion technique. While several different crystallization conditions were obtained, only one set of conditions yielded crystals suitable for X-ray diffraction analysis. These crystals grow as diamond-shaped wedges, with unit-cell parameters a = 50.92, b = 133.99, c = 70.88 Å, a = β = γ = 90°. The crystals belong to space group P2₁2₁2 and diffract to a minimum d spacing of 2.3 Å on a MAR345 image plate with a Rigaku RU-200 rotating-anode X-ray generator. On the basis of density calculations, two monomers are predicted per asymmetric unit (Matthews coefficient, V_M = 2.37 ų Da^-1), with a solvent content of 48%.