Purification, identification and preliminary crystallographic studies of a 2S albumin seed protein from Lens culinaris

Lens culinaris (lentil) is a widely consumed high-protein-content leguminous crop. A 2S albumin protein (26.5 kDa) has been identified using NH₂-terminal sequencing from a 90% ammonium sulfate saturation fraction of total L. culinaris seed protein extract. The NH₂-terminal sequence shows very high homology to PA2, an allergy-related protein from Pisum sativum. The 2S albumin protein was purified using a combination of size-exclusion and ion-exchange chromatography. Crystals of the 2S seed albumin obtained using the hanging-drop vapour-diffusion method diffracted to 2.5 Å resolution and were indexed in space group P4₁ (or P4₃), with unit-cell parameters a = b = 78.6, c = 135.2 Å.