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.
Isolation and characterization of two novel calcium-dependent phospholipid-binding proteins from bovine lung