Role of spectrin in cross bonding of the red cell membrane.

Membrane cross bonding--an adhesion between opposing areas of the cytoplasmic face of the red cell membrane--was achieved by treating red cells with heat, diamide, N-ethymaleimide, urea, or by ATP depletion in conjunction with cell shrinking. Membrane cross bonding could be recognized by the shape of the cells upon swelling. Quantitated by the percentage of cross-bonded red cells the effectivity of the treatments decreased in the order given above. Cross bonding was hardly reversible by reducing the diamide-induced S-S bonds with dithioerythritol. The effect of heat and urea treatment as well as ATP depletion was partly reversible. Transmission electron micrographs of the cross-bonded region showed basically parallel membranes. The distance between the respective phospholipid bilayers varied between 40 and 120 nm from cell to cell. Hb-free ghosts prepared from diamide-treated red cells could also be cross bonded. The following conclusions are drawn: spectrin provides the molecular cross link in membrane cross bonding. Aggregation and enrichment of spectrin in the cross-bonded region are probably involved in membrane cross bonding.