Purification, crystallization and preliminary crystallographic study of a Kunitz-type trypsin inhibitor from Delonix regia seeds.

The Kunitz-type trypsin inhibitor from seeds of Flamboyant (Delonix regia) has been purified to homogeneity and plate-like crystals suitable for X-ray analysis have been grown by the hanging-drop method using PEG 6000 as a precipitant. The crystals belong to space group P2(1)2(1)2(1) with unit-cell parameters a = 32.15, b = 69.39, c = 72.54 A. X-ray diffraction data have been collected to 2.95 A resolution. The structure has been solved by molecular replacement using the known structures of trypsin inhibitors from Erythrina caffra seeds (PDB code 1tie) and from soya beans (Glycine max; PDB code 1ba7) as search models.