The typing of group-specific component (Gc protein) in human blood stains

It is known that the typing of group-specific component (Gc protein) in human blood stains is difficult since Gc protein of the extracts of blood stains migrates more anodally to the α₁-globulin region in agar-gel immunoelectrophoresis, while Gc protein in liquid blood normally migrates to the α₂-globulin region. We have reported that the Gc protein found in the α₁-region is the result of binding of actin to Gc protein (Shinomiya, K., Kimura, H., Yoshida, K., and Shinomiya, T., J. Biochem., 92 (1982) 1163–1171, which renders it difficult to determine the Gc-phenotypes in the blood stains. On the basis of the above findings, we developed the method of phenotyping the Gc protein of human blood stains by agar-gel immunoelectrophoresis. Since the binding activity of actin to Gc protein is lost after treatment with a high concentration of guanidine HCl, the extracts of blood stains were treated with 4 M guanidine HCl to dissociate Gc protein and actin and then dialyzed to remove guanidine HCl. By this method we are able to determine the phenotypes of Gc protein in blood stains. The method we have developed is a useful tool in the forensic laboratory.