CD46, also known as membrane cofactor protein isoform 14, is a type 1 membrane protein that plays an important inhibitory role in the complement system. It is expressed in white blood cells, platelets, epithelial cells, and fibroblasts. The importance of CD46 to complement regulation is underscored by the observation that genetic loss of CD46 leads to development of atypical hemolytic-uremic syndrome, a disease characterized by uncontrolled complement activation. Recombinant human CD46, fused to His-tag at C-terminus, was expressed in insect cell and purified by using conventional chromatography techniques.