Purification and characterization of a lectin from Erythrina americana by affinity chromatography

Abstract

A lectin from the seeds of Erythrina americana Mill has been purified by affinity chromatography with a human type O red blood cell stroma column. In its monomeric form the lectin, which is a glycoprotein with a 7% sugar content by weight, has a molecular weight of 30 000. Ultracentrifugation analysis indicates that the lectin is a dimer with a molecular weight of 57 000 and a S w,20 value of 4.1. Isoelectric focusing reveals the presence of two major molecular components with pI values of 6.3 and 6.6. The lectin is characterized by a high content of leucine, tyrosine, phenylalanine and lysine, a low content of histidine, arginine and methionine, and the absence of cysteine. The composition of the lectin saacharidic portion shows N- acetyl- d- glucosamine , mannose, fusoce and xylose in a molar ratio of 4:3:1:1, respectively. The hemagglutinating activity of the lectin lacks species-specificity, is not modified by treatment with 0.1 M ethylenediamine tetraacetic acid in 1 M acetic acid, and is abolished by galactose, lactose and lactosaminic-containing oligosaccharides or glycosylpeptides. Moreover, N-glycosidically bonded oligosaccharides composed of tri or tetra-antennary structures, derived from fetuin and orosomucoid, with galactose residues in terminal position, are much better inhibitors.