Preliminary x-ray diffraction characterization of crystalline rat liver dihydropteridine reductase

The pyridine dinucleotide-dependent dihydropteridine reductase from rat liver has been crystallized from various inorganic salts and from polyethylene glycol/ethanol mixtures using a vapor diffusion method. The crystal form most amenable to x-ray diffraction studies is monoclinic, space group C2, a = 224.3 A, b = 46.5 A, c = 94.9 A, beta = 99.0 degrees with two molecules in the crystallographic asymmetric unit. These crystals grow to over 1 mm in length, diffract to at least 2.3 A resolution, and are relatively stable to irradiation with x-rays.