Isolation of the third component of mouse complement.

The third component of mouse complement has been purified to homogeneity from pseudoglobulin by two chromatographic steps involving sequential cation- and anion-exchange chromatography. Mouse C3 is a beta-glycoprotein of m.w. 210,000 consisting of two nonidentical, disulfidelinked polypeptide chains of m.w. 130,000 and 75,000, respectively. The properties of this molecule and its proteolytic fragments closely resemble those of human C3.