Recombinant human erythropoietin: purification and analysis of carbohydrate linkage

Erythropoietin was purified to homogeneity from the culture medium of a baby hamster kidney cell line stably transfected with a human erythropoietin gene. A three-step procedure was used, which included affinity chromatography, ion-exchange chromatography, and reverse-phase chromatography. Purity of the protein was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and amino-terminal sequence analysis. Overall recovery was 35%. The biological activity of purified recombinant erythropoietin was similar to that of the native hormone in vitro. The purified recombinant hormone contained N-linked carbohydrate at residues 24, 38, and 83, and and O-linked carbohydrate at residue 126.