VARIABILITY OF THE LOW-MOLECULAR-WEIGHT GLOBULIN, CONGLUTIN-DELTA, WITHIN LUPIN SPECIES

Conglutin delta, a 2S globulin, was purified and compared in six speci es or varieties of lupin seeds. A common pattern is suggested, present in all species, corresponding to a protein which could exist as a mon omer or a dimer. The first farm contains one subunit, from 11 to 16.2 kDa, according to the species. It possesses a quaternary structure clo sely related to conglutin delta 1 and was previously described in the narrow-leaved lupin, The second form contains two similar subunits (23 to 26 kDa) and could be the conglutin delta 2. These two subunits are associated even when SDS is used and are probably disulfide-linked su bunits. Each subunit is composed of two disulfide-linked polypeptides. One is acidic with molecular weight from 14 to 17.3 kDa and the secon d is acidic to neutral, from 2.4 to 4.5 kDa. Three species (L. luteus, L. arboreus and L. pilosus) present a supplementary subunit, with dif ferent molecular weight and pi than that previously described and whic h never associates in a dimer form. It has been purified in L. luteus. When native, this protein is oligomeric. The subunit of 12 kDa in thi s species is composed of a polypeptide of 9 kDa (pi 4.5) disulfide-lin ked to one of 3 kDa (pi 6.5). This supplementary protein remains partl y associated with the first in the yellow lupin (L. luteus). It probab ly corresponds to a new protein, different from conglutin delta.