Isolation and characterization of the folate-binding protein from cow's milk

Abstract

The folate-binding protein from cow's milk has been purified in milligramme scale by combination of ion-exchange chromatography and affinity chromatography. The molecular weight has been determined by sedimentation equilibrium ultracentrifugation and found to be 30,000±2,000. The amino acid composition is compatible with this value. The molecule contains six disulphide bridges and no free SH-groups. The three per cent carbohydrate content was accounted for by six glucosamine residues per mole of protein. About 50 per cent of the amino acid sequence has been delineated, including the N-terminal sequence and the C-terminal sequence. Isoelectric focusing gave rise to four major peaks with isoelectric points ranging from 8.5 to 7.6, but no heterogeneity was observed in the sequence. © 1979 Carlsberg Laboratory.