Membrane proteins related to water transport in human erythrocytes

Abstract

CLASSICAL interpretations of the mechanism of water transport across mammalian red cell membranes assume the existence of aqueous membrane pores^1–3. As the permeability coefficient to water measured under an osmotic pressure gradient is usually significantly higher than the corresponding value measured under diffusional flow, the human red cell membrane is thought to act both as a selective solvent and a molecular sieve. Its ability to function as a molecular sieve depends on the existence of the pores, which could be assembled from aggregates of integral membrane proteins which span the membrane⁴. It is generally agreed that at least two proteins span the human red cell membrane^5–7. Using polyacrylamide gel electrophoresis we have found that a band which contains one of these proteins is selectively labelled by a water-transport inhibitor.