Seed proteins of Lupinus mutabilis

Lupinus mutabilis sweet seeds possess the highest levels of oil and protein of all domesticated lupin species. However, no information has been published concerning the structure of its storage proteins. An electrophoretic comparative study of the seed storage protein composition of L. albus cv. Multolupa, L. mutabilis cv. Potosi, and L. mutabilis cv. Inti is reported. Small differences were observed between the two L. mutabilis cultivars, but broad differences were detected when the two species were compared. L. mutabilis seeds were considerably richer in total nitrogen, total protein, and total globulins but were poorer in albumins than L. albus. Besides, L. mutabilis total globulins showed less electrophoretic mobility under nondenaturing conditions when compared with L. albus Total albumins and total globulins produced very different electrophoretic patterns in the two Lupinus species when analyzed by denaturing, reducing, or nonreducing electrophoresis. When the three individual conglutins were considered, differential results were obtained. γ-Conglutin structure seems to be identical in all cultivars investigated. Subunits and polypeptide chains of α-conglutin showed some degree of heterogeneity among the three cultivars analyzed. β-Conglutin possessed the greatest structural variation, being composed of over 20 polypeptide chains in L. albus, covering a broad range of molecular masses (15-65 kDa). Six to seven major polypeptide chains in L. mutabilis β-conglutin were observed, covering a limited range of molecular masses (50-67 kDa).