EN
There are two established pathways linking the membrane cytoskeleton of the red blood cell to integral proteins of the membrane. We review the characteristics of these interactions and give reasons for believing that they are insufficient to engender the exceptional stability and elastic properties that characterise the native membrane. We show that in a model system, consisting of a phospholipid monolayer, spread at the air-water interface, with the major structural protein of the membrane cytoskeleton, spectrin, added to the aqueous subphase, an energetically important interaction occurs between the protein and the lipid. This reveals itself as an area contraction, occurring at high surface pressures that do not permit penetration of the protein to the airwater interface. The interaction requires the presence in the lipid layer of the inner-leaflet component, phosphatidylserine. Binding of spectrin to the lipid is accompanied by a large increase in surface viscosity, implying that this interaction alone can exert a major effect on the mechanical properties of the membrane.