Phaseolus limensis agglutinin (LBA) is isolated from lima bean seeds and purified by affinity chromatography. LBA is composed of 30,000 Da subunits, of which two are joined by a disulfide bond. Each subunit contains a cysteine residue which is required for both it’s carbohydrate- and metal-ion-binding activities. It has a carbohydrate specificity of terminal GalNAcα(1,3)Gal that elutes with N-acetylgalactosamine. LBA agglutinates blood group A erythrocytes.
Colloidal gold can be used to visualize localization of specific saccharide moieties and examine the distribution of plasma membrane glycoproteins based on the binding pattern of Phaseolus limensis Lectin (LBA). Colloidal gold labeled lectins can be viewed via electron microscopy.