Vicia villosa lectin or agglutinin (VVL/VVA) is isolated from hairy vetch seeds. It is a tetramer composed of four subunits and a molecular weight of 144 kDa. It has an isoelectric point between pH 5.5 and pH 6.2. VVL consists of A and B subunits, with a dominant isolectin that appears to be B subunit-rich. A4 isolectin agglutinates specifically A1 erythrocytes, B4 isolectin agglutinates Tn exposed erythrocytes but does not agglutinate A, B, or O-erythrocytes, and A2B2 isolectins display properties characteristic of both A4 and B4 isolectins.

VVLB4 binds specifically to GalNAc structures, and studies suggest that this lectin binds only to the terminal GalNAc structure, rather than both the internal and terminal structures. VVL interacts with the terminal alpha-linked Gal over GalNAc, and displays a weaker binding to alpha-linked GalNAc and Gal compared to alpha-linked counterparts. Evidence suggests that this lectin also may require specific amino acid sequences at the receptor site of glycosylation. The disaccharide galactosyl (α-1,3) N-acetylgalactosamine is also a potent inhibitor of this lectin.