The Seed Proteins of Cowpea (Vigna unguiculata L. Walp.)

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Abstract
Cowpea (Vigna unguiculata L. Walp.) seeds were shown to contain a major globulin protein of mol. wt. 170 000 which was heterogeneous; two components could be separated by gel electrophoresis at pH 4.0, one containing subunits of mol. wt. 52 000 and 58 000, the former predominating, the other containing subunits of mol. wt. 52 000, 58 000, and 63 000 in roughly equal amounts. The 58 000 and 63 000 mol. wt. subunits contained covalently bound carbohydrate. All three subunit types were shown to contain extensive sequence homology by tryptic peptide mapping; cleavage with cyanogen bromide also indicated homology between subunit types. The 52 000 and 58 000 mol. wt. subunits were shown to be heterogeneous within each size class. The major globulin protein is possibly a trimer, three subunits from the various types of 52 000, 58 000, and 63 000 mol. wt. subunits assembling to form a molecule. Of the other proteins identified in cowpea seeds, one was a globulin protein of mol. wt. 300–400 000 containing disulphide-linked pairs of subunits of mol. wt. 62 000 and 18 500. Another globulin protein contained disulphide-linked dimers of a 56 000 mol. wt. subunit. A major albumin protein was a monomer, subunit mol. wt. 105 000; other albumin proteins present in significant amount (subunit mol. wts 32 000, 22 500, and lower) had lower mol. wts.