The IgG binding function of the normal red cell plasma membrane: identification of integral polypeptides that bind IgG.

Non-immune IgG binds to red cell integral membrane proteins obtained by mild alkaline extraction of ghosts. Detergent gel chromatography and electrophoretic analyses of IgG-membrane protein complexes obtained by nonionic detergent solubilization and affinity binding to protein A indicate that three polypeptides participate in the binding of IgG. These have apparent molecular weights of 90 000, 44 000 and 22 000 and are present in a 1:3:0.9 stoichiometry. Evidence obtained indicates that the major sialoglycoproteins are not involved in this type of binding.