Crystallization and preliminary X-ray diffraction studies of human epidermal growth factor

Human epidermal growth factor (hEGF), a 6.2 kDa protein of 53 amino acids w ith three internal disulfide bridges, has been crystallized by the hanging- drop method. hEGF crystallizes in space group P3(1)21 (or P3(2)21) using Mg Cl2 as precipitant, with unit-cell parameters a = b = 61.4, c = 87.0 Angstr om. Another type of crystal, obtained using NaCl as precipitant, belongs to a tetragonal point group and has unit-cell dimensions a = b = 102.5, c = 1 66.6 Angstrom. The trigonal crystals with the smaller unit cell diffract X- rays better and a native data set from a single crystal has been collected to 3.0 Angstrom resolution.