The Phaseolus acutifolius (Tepary Bean) lectin was purified by affinity chromatography using glutaraldehyzed membranes from blood group O erythrocytes. TBL/EsL is a tetrameric glycoprotein of 121 kDa with 10% sugar by weight composed of four subunits of 30 kDa, as determined by SDS-PAGE. The lectin is composed of four isolectins. The lectin and its isolectins have homology to the PHA leucoagglutinin-precursor. TBL/EsL and its four isolectins agglutinate erythrocytes without serological specificity and show mitogenic activity on human leukocytes. This lectin is not inhibitable by simple sugars. However, the specificity of the lectin and its isoforms is mainly addressed toward galactose residues present in bi- or triantennary N-acetyllactosamine-type glycans.
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