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Published February 2004 | public
Journal Article

Molecular Mechanisms of Electrogenic Sodium Bicarbonate Cotransport: Structural and Equilibrium Thermodynamic Considerations

Abstract

The electrogenic Na⁺-HCO₃⁻ cotransporters play an essential role in regulating intracellular pH and extracellular acid-base homeostasis. Of the known members of the bicarbonate transporter superfamily (BTS), NBC1 and NBC4 proteins have been shown to be electrogenic. The electrogenic nature of these transporters results from the unequal coupling of anionic and cationic fluxes during each transport cycle. This unique property distinguishes NBC1 and NBC4 proteins from other sodium bicarbonate cotransporters and members of the bicarbonate transporter superfamily that are known to be electroneutral. Structure-function studies have played an essential role in revealing the basis for the modulation of the coupling ratio of NBC1 proteins. In addition, the recent transmembrane topographic analysis of pNBC1 has shed light on the potential structural determinants that are responsible for ion permeation through the cotransporter. The experimentally difficult problem of determining the nature of anionic species being transported by these proteins (HCO₃⁻ versus CO₃²⁻) is analyzed using a theoretical equilibrium thermodynamics approach. Finally, our current understanding of the molecular mechanisms responsible for the regulation of ion coupling and flux through electrogenic sodium bicarbonate cotransporters is reviewed in detail.

Additional Information

© 2004 Springer-Verlag New York Inc. Received 01 August 2003; Revised 23 October 2003. Issue Date February 2004. This work was supported by DK63125, DK58563, and DK07789, DK60071, the Max Factor Family Foundation, the Richard and Hinda Rosenthal Foundation and the National Kidney Foundation of Southern California J891002.

Additional details

Created:
August 22, 2023
Modified:
October 19, 2023