ABSTRACT
Schematic illustration of interactions between the red cell membrane and its underlying skeleton
These results led us to examine the region of GPC/D involved in the binding. Three synthetic peptides were prepared corresponding to the entire cytoplasmic domain of GPC/D. One peptide (GPC-1) corresponds to GPC residues 112-128, GPC-2 to residues 99-111 and GPC-3 to residues 82-98. Each peptide was tested for its ability to inhibit the binding of purified protein 4.1 to protein 4.1 depleted normal membranes. GPC-3 was by far the most potent inhibitor (up to 80% inhibition of protein 4.1 binding). Furthermore, GPC-3 was shown to bind directly to purified protein 4.1. GPC-3 also bound directly to Leach phenotype membranes prior to protein 4.1 depletion but not to normal membranes or Leach membranes depleted of protein 4.1, suggesting that the GPC-3 binding site on protein 4.1 is not occupied in Leach phenotype membranes. These results led us to conclude that direct interaction between protein 4.1 and GPC/D is mediated by the protein sequence on GPC/D located within residues 82-98 (6).
