Immunochemical Studies on Structural Proteins of the Red Cell Membrane

Up to one third of the membrane proteins from bovine, ovine and human red cells were solubilized similarily by water pH 9.5, aqueous pyridine, ATP‐mercaptoethanol solutions or urea pH 11. The proteins are heterogeneous but show some common features independent of the extraction method applied. The remaining insoluble proteins are rather different and contain most of the lipids and of the surface antigens. In the extracts mainly a common membrane‐specific antigen of high anodic mobility was demonstrated which contains neither sialic acids nor lipids. This antigen is species‐specific and is not located on the membrane outside. It is not exposed to the surface after proteolytic treatment of intact red cells. The extracts are contaminated by traces of plasma proteins and surface antigens. The membrane antigen can be correlated to a characteristic double band demonstrable in the stroma by disc electrophoresis in the presence of sodium dodecylsulfate. The molecular weights were estimated as 190 000 and 210 000, respectively. Evidence is provided that these components represent aggregates.