Purification of lectins from Robinia pseudoacacia L root-tips

The presence of lectins in Robinia pseudoacacia root-tip extracts was demonstrated by horse erythrocyte agglutination and aggregation of (neo)glycoprotein-coated beads. Two lectins were purified from a crude protein extract by ion-exchange and affinity chromatography. A mixture of lectins was obtained by cation-exchange chromatography on a CM-Trisacryl column. Rabinia pseudoacacia root agglutinin II (RPrAII) was further purified by specific elution from a GalNAc-BSA-Sepharose-4B column. Material passing through the GalNAc-BSA-Sepharose-4B column was still active as determined by erythrocyte agglutination, and aggregated orosomucoid-coated beads, this material was further purified by affinity chromatography on an orosomacuoid-Sepharose-4B column. Elution with 50 mM HC1 at pH 1.5 led to the purification of the second lectin referred as Rabinia pseuctoacacia root agglutinin I (RPrAI). Biochemical analysis suggests that RPrAI is a heterodimer made up of M(r)29 000 and 31 000 subunits whereas RPrAII is a homodimer made up of M(r) 30 000 subunits, and that both lectins are glycoproteins. N-terminal sequences were determined for both lectins and compared with those deduced from cDNA clones encoding bark and seed lectins. Our results suggest that root lectins are not strictly identical with, but closely related to the Robinia pseudoacacia seed and bark lectins. (C) 1997 Elsevier Science Ireland Ltd.