Further studies on mitogenic components of Phaseolus vulgaris phytohemagglutinin: Subunit structure

The mitogens of a phytohemagglutinin from red kidney beans contain two types of subunits. These subunits were isolated in fairly large scale using a preparative gel electrophoresis in sodium dodecyl sulfate-urea. One type (α) was made up of a single subunit species of MW 35,000 (a dimer at pH 7), and this molecule kept its mitogenic activity after sodium dodecyl sulfate treatment. The other type (β) which was mitogenically inactive after sodium dodecyl sulfate treatment, appeared to consist of two kinds of subunits with molecular weights of 35,500 and 36,500. Analysis for amino acids and carbohydrates, mapping techniques for tryptic and chymotryptic peptides and molecular weight determination have established structural differences between the two subunits. However, terminal amino acids (NH 2 - and COOH-) of both subunits were identical, suggesting that they had closely related primary structures.