Change in binding properties of folate-binding protein in cow's whey due to removal of a cofactor during affinity chromatographic purification.

The folate-binding protein in cow's whey was purified by affinity chromatography on folate or methotrexate-AH-Sepharose 4B. A change in basic binding properties of the protein occurred probably due to the fact that material removed during affinity chromatography contains a cofactor of great importance to folate binding.