Isolation and characterization of galectin-1 binding proteins from human placenta

Abstract

Galectin-1 binding proteins were isolated from human placenta by affinity chromatography on a column with immobilized endogenous lectin. The molecular masses of the isolated proteins of 170, 67 and 56 kDa were estimated by gel filtration and SDS-PAGE. These proteins were characterized as galactose-containing glycoproteins, based on their reactivity with Ricinus communis agglutinin. In addition, sialylated- lacto-N-fucopentaose II was detected in the 170 kDa protein, using anti CA 19-9 monoclonal antibodies. The interaction of the isolated proteins with human placental galectin-1 was investigated by a solid phase binding assay using asialofetuin as the glycoprotein ligand. The 67 kDa and 56 kDa proteins were found to inhibit galectin-1 binding of asialofetuin, whereas the 170 kDa protein had the opposite effect. It caused an increase in the binding of asialofetuin, suggesting a positive cooperative binding.

Keywords

• galectin-1
• human placenta
• affinity chromatography
• rca i
• ca19-9