Structural and genetical studies on legumin of pisum sativum L. and vicia faba L.

Abstract

studies have been made on the structure and genetics of the major seed storage protein, legumin, in Pisum sativum L. and Vicia faba L. Two dimensional gel electrophoresis, using non-reducing conditions in the first dimension and reducing conditions in the second dimension, used in conjunction with other different combinations of various electrophoretic techniques, has been found to be of great value in elucidating the structure of legumin. In both these legumes, legumin has been shown to be composed of a number of subunit pairs of different molecular weights, Vicia legumin (subunit pairs of mol. wt. 37,000-79,000) being more heterogeneous in this respect than the Pisum legumin (subunit pairs of mol. wt. 35,000-58,000). The subunit pairs are associated into hexameric molecules by non-covalent interactions? there exist a number of different molecular forms containing the subunit pairs in different combinations. Each subunit pair contains a large, relatively acidic subunit (mol. wt. 22700-58,000 in Vicia and 24,500-43,000 in Pisum? pI range 4.6-6.1 in Vicia and 4.85-6.15 in Pisum) and a smaller, relatively basic subunit (mol. wt. 21,000-23,000 in Vicia and 20,700-22,700 in Pisum; pI range 8.2-8.5 in Vicia and 6.2-8,0 in Pisum) linked covalently by one or more disulphide bonds. Genetic studies on Pisum sativum have shown that various legumin subunits all followed monogenic inheritance the alleles showing co-dominance with respect to each other. The genes for some but not all different types of legumin subunits have been shown to be inherited independently. The gene(s) for the acidic subunits of the major legumin subunit pair (s) is located 15 map units distant from the t l locus on the side away from the r locus on chromosome 7. A further storage protein gene has been mapped in that the gene for the convicilin subunits is strongly linked to the locus k on chromosome 2.