EPO, also known as erythropoietin, is a glycoprotein hormone in the type I cytokine family and is related to thrombopoietin. Its three N-glycosylation sites, four alpha helices, and N- to C-terminal disulfide bond are conserved across species. It is primarily produced in the kidney by a population of fibroblast-like cortical interstitial cells adjacent to the proximal tubules. This protein can be found in the plasma and regulates red cell production by promoting erythroid differentiation and initiating hemoglobin synthesis. It also has neuroprotective activity against a variety of potential brain injuries and anti-apoptotic functions in several tissue types. Recombinant human EPO, fused to His-tag at C-terminus, was expressed in insect cell and purified by using conventional chromatography techniques.