title: The membrane attack mechanism of complement: the three polypeptide chain structure of the eigth component (C8).
abstract: The purification of human C8 in milligram quantities from outdated human serum was achieved by ammonium sulfate precipitation (37.5-50% saturation) and ion exchange column chromatography employing CM-32 cellulose and QAE-Sephadex. The yield of C8 activity ranged from 2-9%, and the average purification was 1,700-fold. Fully reduced C8 was shown by SDS polyacrylamide gel electrophoresis to have three polypeptide chains which were present in equimolor ratios: alpha, 77,000 daltons; beta, 63,000 daltons; and gamma, 13,700 daltons. C8 denaturation by SDS and urea in the absence of reducing agents revealed two noncovalently linked subunits: alpha-gamma, 99,000 daltons, and beta, 75,000 daltons.
mesh_terms: D003185:Complement C8 / Q000302:isolation & purification / Q000378:metabolism*; D003165:Complement System Proteins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D008970:Molecular Weight; D011487:Protein Conformation; D014443:Tyrosine
chemical_list: D003185:Complement C8; D014443:Tyrosine; D003165:Complement System Proteins