Elucidation of the antigenic architecture of the Acholeplasma laidlawii cell membrane by immunoabsorption in combination with crossed immunoelectrophoresis.

Immunoabsorption in combination with crossed immunoelectrophoresis was used for elucidation of the antigenic architecture of the Acholeplasma laidlawii cell membrane. When cells were grown in a medium containing cholesterol and unsaturated fatty acids, the cell membranes became fragile. Membrane proteins or membrane fragments, which under some conditions seemed to be enriched in specific proteins (especially protein T2), were released into the growth medium. Therefore, most of the experiments were performed with cells grown in a cholesterol-free medium. Antigenic determinants of ectoproteins were expressed to a greater extent on the exterior face of the membrane when the cells were harvested in the early phase of the growth cycle. Furthermore, for the proteins t1a and t1b, which are membrane proteins of high molecular weight, antigenic determinants were expressed on both the exterior and the cytoplasmic faces of the membrane. Antigenic determinants of protein T4b were expressed on the cytoplasmic face of the membrane. For the flavoprotein T4a, antigenic determinants were expressed exclusively on the cytoplasmic face. All antigenic determinants of the protein T2 probably were expressed on the exterior face of the membrane, whereas no antigenic determinants of protein T3 were exposed on either face of the membrane.