Phospholipid composition of human erythrocyte spectrin.

Human erythrocyte spectrin, which has been extracted at low ionic strength and precipitated at pH 5.1, contains 0.025 mumoles phospholipid/mg protein. The composition of the spectrin-phospholipids differs from that of the erythrocyte membrane. A remarkable similarity was found between the composition of the "available" phospholipids of the inner leaflet of the membrane bilayer and the spectrin-associated phospholipids. Rebinding studies with 125I-labeled spectrin show that the labeled spectrin binds preferentially to the cytoplasmic side of the membrane and that this binding is influenced by protein perturbations.