Some properties of carbohydrate-binding proteins (lectins) solubilized from cell walls of Phaseolus aureus

From the cell walls of nongrowing segments of mung bean hypocotyls two protein fractions can be solubilized which show carbohydrate binding properties as measured with the hemagglutination assay. The extracts show appreciable binding activity only if the walls are treated with boiled cytoplasmic supernatant prior to extraction; Mn(2+) is only partly effective in a similar way. Hydrolase activity in the extracts is strongly diminished by sequential washing of the walls with sodium dodecylsulphate; extensive washings, however, result in inactivation of the hemagglutination activity. The carbohydrate binding activity of both extracts is strongly diminished towards acidic pH-values and is inhibited by D-galactose and γ-D-galactonolactone. The possible involvement of the binding proteins in extension growth is discussed.