Cl(-)-ATPases: Novel primary active transporters in biology

Five widely documented mechanisms of chloride transport across plasma membranes are anion-coupled antiport, sodium and hydrogen-coupled symport, Cl(-)channels, and an electrochemical coupling process. No genetic evidence has yet been provided for primary active chloride transport despite numerous reports of cellular Cl(-)-stimulated ATPases co-existing, in the same tissue, with uphill chloride transport that could not be accounted for by the five common chloride transport processes. Cl(-)-stimulated ATPase activity is a common property of practically all biological cells with the major location being of mitochondrial origin. It also appears that plasma membranes are sites of Cl(-)-stimulated ATPase activity. Recent studies of Cl(-)-stimulated ATPase activity and active chloride transport in the same membrane system, including liposomes, suggest a medication by the ATPase in net movement of chloride up its electrochemical gradient across plasma membranes. Further studies, especially from a molecular biological perspective, are required to confirm a direct transport role to plasma membrane-localized Cl(-)-stimulated ATPases. J. Exp. Zool. 289:215-223, 2001.