The sodium pump: a ghost story

Evidence that the sodium plus potassium activated adenosinetriphosphatase ((Na + K)-ATPase) is present and functions normally in a red blood cell ghost is summarised. The case is then argued that since ghost move neither sodium nor potassium against an electrochemical gradient, the (Na+ + K)-ATPase is not in itself sufficient to generate transmembrane gradients of sodium and potassium ions. If it is not sufficient in ghost, then it cannot be sufficient in intact cells, but most somehow work co-operatively with the cytoplasm. An alternative hypothesis to that of carrier-mediated transported is then proposed, and shown to be consistent with data on intact cells, membrane homogenates, ghosts, and membrane vesicles derived from bacteria.