RRM2, also known as ribonucleotide reductase M2, is an enzyme that catalyzes the formation of deoxyribonucleotides from ribonucleotides. This protein plays a critical role in regulating the total rate of DNA synthesis so that DNA to cell mass is maintained at a constant ratio during cell division and DNA repair. Recombinant human RRM2 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.