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 moles 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 spectrinassociated phospholipids. Rebinding studies with^{1 2 5}I-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.