A simple preparative procedure to extract and purify protein G from group G streptococci.

A rapid method for the solubilization of the bacterial type III Fc binding protein, protein G, from a group G streptococcus is described. Treatment of intact bacteria with cyanogen bromide results in the solubilization of a homogeneous Mr approximately 50,000 protein which retains IgG and human serum albumin binding properties. The solubilized protein could be purified to homogeneity by molecular sieving chromatography and retained all of the functional properties of the native protein.