CRYSTALLIZATION AND PRELIMINARY-X-RAY DIFFRACTION STUDIES OF PANCREATIC SPASMOLYTIC POLYPEPTIDE

Pancreatic spasmolytic polypeptide (PSP) isolated from porcine pancreas has been crystallized by the hanging drop vapour diffusion method. The crystals belong to the space group I222 or I212121 with cell dimensions a = 181·9 A ̊, b = 54·5 A ̊, c = 72·9 A ̊. The crystals diffract to at least 2·5 Å resolution and the asymmetric unit contains two molecules (Vm = 3·9 A ̊3/Da) with a solvent content of 68% as determined by density measurements of the crystals. The self-rotation function suggests that the two molecules within the asymmetric unit are related by a 2-fold axis at either 30 ° or 60 ° from a in a plane perpendicular to the b axis. © 1992.