Crystallization and preliminary X-ray study of saporin, a ribosome-inactivating protein from Saponaria officinalis

Single crystals of the protein saporin isolated from the seeds of S. officinalis have been grown by the vapor-diffusion method using ammonium sulfate as precipitant. The crystals are tetragonal, space group P4₁22 (P4₃22), with cell dimensions a = b = 67.53 and c = 119.67 Å, and diffract to 2.0 Å resolution on a rotating-anode X-ray source. The asymmetric unit contains one molecule, corresponding to a volume of the asymmetric unit per unit mass (V_m) of 2.38 Å³ Da^-1.