Isolating and characterising a lectin from Galactia lindenii seeds that recognises blood group H determinants

A lectin was isolated from Galactia lindenii seeds and characterised. The lectin, purified by affinity chromatography, readily agglutinated O(H) human erythrocytes and interacted weakly with rabbit and rat erythrocytes. Specificity towards blood group H-type determinants was established; among them H-type 2 (α-l-Fuc (1–2)-β-d-Gal (1–4)-β-d-GlcNAc-O-R) was recognised by the lectin. The binding to the glycoconjugate was partially inhibited by GalNAc and Me-β-Gal. The protein is an M=104,256 tetramer which dissociates into identical M=26,064 subunits under non-reducing conditions. Its amino acid composition, pI, A1%, and N-terminal sequence (23 residues) were determined. The N-terminal region showed a unique sequence found hitherto only in some lectins (designated type-II) from the Dioclea genus. This work presents the evidence concerning a distinct type of lectin found in the Diocleinae tribe able to recognise the H-type 2 human blood group determinant and clearly different from the Glc/Man-specific lectins. The protein is a potential tool in cellular and histochemical studies.