ISOLATION AND CHARACTERIZATION OF A BETA-GALACTOSIDE-BINDING PROTEIN (14 KD) FROM RAT-LIVER NUCLEI

A soluble carbohydrate-binding protein with galactoside-binding properties (CBP14) was isolated from liver nuclei of adult rats. Proteins were extracted from membrane-depleted nuclei; they contained 3 major fractions (M(r) 43,000, 14,000 and 10,000) which reacted with antibodies raised against human placental beta-galactoside-binding lectin (HP 14) as well as with asialofetuin (ASF). Enrichment (72- to 143-fold) of CBP14 was carried out by affinity chromatography, using anti-HP14 antibodies and ASF as consequent ligands. CBP14 retained by affinity column chromatography was characterized by the molecular mass, haemagglutinating activity and immunochemical cross-reactivity. By fluorescence technique using fluorescein-labelled neoglycoprotein (carrying lactose) as a probe, lactose-binding protein(s), e.g. the CBP14 described here, can be detected in a homogeneous staining pattern within the entire nucleus of CV-1 cells in the stationary phase of the cells. In case of logarithmically proliferating cells the lactose-binding protein(s) are arranged in a spot-like pattern along the rims of the cell nuclei. The putative ligand for the CBP14 is associated with the nuclear surface, irrespective of the proliferation state of the cells.