Molecular Weight of Legumin From Pisum sativum

Abstract

There have been many physicochemical studies of legumin, one of the major storage globulins isolated from pea seed. The more recent literature values for the molecular weight of this protein are in the range 390 000-420 000. These results are not consistent with the subunit molecular weight of legumin determined by dodecyl sulfate-polyacrylamide gel electrophoresis, if a hexameric model is assumed. We have measured the molecular weight of a highly purified sample of Pisum legumin by meniscus depletion sedimentation equilibrium and have found a value of 350 000 ± 10 000. Since the oligomeric protein is homogeneous with respect to molecular weight, the heterogeneity reported for the subunit polypeptides, using various conditions of electrophoresis, presumably reflect differences in charge and amino acid composition. The molecular weight of legumin is significantly greater than the value of 325 000 found for cucurbitin, the equivalent crystalline protein isolated from pumpkin seed.