Crystallization and preliminary X-ray analysis of Gc, the vitamin D-binding protein in serum

The vitamin D-binding protein, Gc, was purified from human serum and crystallized using the hanging-drop method. The best crystals were grown from 28% polyethylene glycol 400 in 50 mM-sodium acetate at pH 4.8. These crystals diffract to 3.4 A and the observed diffraction is consistent with orthorhombic space groups P4(1) and P4(3). The unit cell parameters were determined to be a = b = 135.5 A and c = 75.6 A.