Electrophoretic Studies of the Seed Proteins of Cowpea, Vigna unguiculata (L.) Walp.

Abstract

Summary The globulin fraction accounted for the major proportion (72%) of the protein extracted from mature cotyledons of cowpea, Vigna unguiculata (L.) WALP. cv. Vita 3. The globulin and albumin fractions were compared by pore-gradient polyacrylamide gel electrophoresis, and component polypeptides were analysed by SDS polyacrylamide disc gel electrophoresis. The major globulin, vignin, consists mainly of non-covalent associations of polypeptides of MW 56,000 and 52,500 daltons. Under reducing conditions, globulin polypeptides of MW 80,000 and 43,000 dissociate and polypeptides of 61,000, 26,500 and 19,000 daltons are formed. Under the same conditions, the major polypeptides of the albumin fraction are distinct from those of the globulin fraction, having sizes estimated to be ca. 100,000, 70,000, 43,000, 35,000, 32,000 and 25,000 daltons. During embryo development there is no clear division into a period of albumin synthesis followed by a period of globulin synthesis; polypeptides representing both fractions were present from the earliest stage analysed, 7 days after anthesis. There are, however, differences in the periods of most rapid net synthesis for individual polypeptides of each fraction.