Structure of Erythropoietin

Initially, erythropoietin is a protein 193-amino acid in length, without biological activity. Shortly before secretion, the N-terminus leader sequence of 27 residues is cleaved, leaving only 166 amino acids. When erythropoietin enters the blood stream, the amino acid arginine is lost, leaving a final sequence of 165 amino acids.

The functional erythropoietin shows two disulfide bridges formed by the amino acid cysteine at position 7 and 161, as well as 29 and 33.

The molecular weight of an erythropoietin peptide backbone is 18.000 Dalton. After undergoing post-translational modification, glycosylation, the molecular weight of erythropoietin becomes 30.000 Dalton. 40% of erythropoietin is composed of three N-linked carbohydrate structures, located at Asp-24, 38, and 83, and one O-linked carbohydrate structure, located at Ser-126.