Expression, purification, crystallization and preliminary X-ray crystallographic analysis of Enpp1

Enpp1 is an extracellular membrane-bound glycoprotein that regulates bone mineralization by hydrolyzing ATP to generate pyrophosphate. The extracellular region of mouse Enpp1 was expressed in HEK293S GnT1^- cells, purified using the TARGET tag/P20.1-Sepharose system and crystallized. An X - ray diffraction data set was collected to 3.0 Å resolution. The crystal belonged to space group P31, with unit-cell parameters a = b = 105.3, c = 173.7 Å. A single-wavelength anomalous dispersion (SAD) data set was also collected to 2.7 Å resolution using a selenomethionine-labelled crystal. The experimental phases determined by the SAD method produced an interpretable electron-density map.