Variability in the Proportion and Type of Subunits in Lupin Storage Globulins

Abstract

The seeds of 12 species of lupin were examined and were found to contain two major globulins, conglutins α and β, while some contained a third minor globulin, conglutin �. There were considerable differences between species in the electrophoretic mobility and proportions of conglutins α and β, and in their subunit composition in terms of the number of components, their molecular weights and the importance of disulphide bonding between them. However, the electrophoretic behaviour and subunit composition of conglutins α and β did appear to be species-specific. Conglutin γ, on the other hand, did not seem to vary in molecular size or electrophoretic mobility within this genus. The 18 cultivars of Lupinus angustifolius examined appeared to be more closely related in terms of the number and size of subunits, although variations were apparent in the relative proportion of these subunits, especially with wild types. It is suggested that this variability in the protein structure of lupin globulins may provide evidence that substantial changes can be induced by genetic selection in the composition of these proteins without upsetting their structure-function relations.