The major albumin proteins from pea (Pisum sativum L). Purification and some properties

Abstract

A scheme is described for the fractionation of pea (Pisum sativum) albumin proteins. By using this scheme, two closely related major albumin proteins have been isolated and purified to homogeneity. The larger protein, designated PMA-L, has Mr approximately 53 000 and consists of two 25 000-Mr subunits, whereas the smaller, PMA-S, has Mr approximately 48 000 and contains two 24 000-Mr subunits. There was no evidence of mixed dimers of the two subunit sizes, despite their close homology as judged by immunological crossreaction, amino acid composition, N-terminal amino acids, tryptic-peptide mapping and CNBr-cleavage products. Both proteins contained significant amounts of sulphur amino acids. The proteins were shown to be located in the soluble cytosol fraction of cotyledon cells and are not significantly degraded on seed germination. Preliminary screening indicates the presence of homologous major albumin proteins in at least three different, though closely related, legume species.