Affinity purified Sambucus nigra lectin (EBL I+II, also known as SNA) is is composed of two ricin-related lectins. EBL I+II is a tetrameric glycoprotein with a recognition of the Neu5Ac(?2-6)Gal or GalNAc linkage in glycoconjugates.
EBL I+II is not blood group specific but it does agglutinate type A erythrocytes more strongly than either B or O cells. Trypsin treated erythrocytes react better than untreated cells. Neuraminidase treated erythrocytes react with this lectin due to the presence of terminal galactose resides. SNA has a broad specificity for both ?- and ?-linked galactose, as well as unrelated sugars such as fucose. It has been determined that the lectin does not bind to glycoproteins or glycolipids containing only terminal ?(2,3)-linked sialic acid residues.
EBL I is composed of an A-chain with enzymatic activity and a B-chain with carbohydrate-binding activity. EBL II consists only of carbohydrate-binding B-chains. EBL I+II induces caspase-dependent apoptosis at low concentrations (nM) order, leading to typical symptoms of cell death in sensitive cells. This effect seems independent from the catalytic activity of the A-chain, but depends on the carbohydrate binding B-chain.