Studies on the major seed proteins of some grain crops

Abstract

The general properties, classification and distribution of plant proteins are discussed within an agricultural context and the protein content and composition of several grain crops are tabulated. The major proteins of legume seeds are salt soluble proteins (i.e. globulins) and the methodology for their extraction, separation and characterisation is reviewed. The structure, location and distribution of legume globulins are described and the properties of various purified legume globulins are compared. The major seed proteins of Pisum sativum are legumin and vicilin and seed globulins with properties similar to those of legumin and vicilin have been extracted from other legumes. The isolation and partial characterisation of vicilin-like proteins from seeds of Phaseolus vulgaris and Vigna vinguiaulata and of legumin-like proteins from these two species and Phaseolus aureus is described. The potential usefulness of the examination of seed proteins by polyacrylamide gel electrophoresis to taxonomic problems in Phaseolus and Vigna is investigated and the data obtained are discussed in relation to recent re-classifications of the species. Procedures for the extraction and partial characterisation of proteins from an archaeological sample of maize grains are described and the proteins from this sample are compared with the proteins from a modern variety of maize. It is suggested that protein data from archaeological samples could be useful in studies of crop plant origins and in cultural studies, and that the procedures employed may be applicable to archaeological samples of other grains. Nutritional aspects of plant proteins are discussed briefly. A possible strategy for the improvement of the sulphur amino acid content of legumes with a relatively low legumin content is suggested and it is demonstrated that polyacrylamide gel electrophoresis may provide a basis for a screening procedure for protein quality in legume breeding programmes.