A universal mechanism for transport and regulation of CPA sodium proton exchangers

Octavian Călinescu and Klaus Fendler 1
  • 1 Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max-von-Laue-Str. 3, D-60438 Frankfurt/Main, Germany
  • 2 Department of Biophysics, Faculty of Medicine, ‘Carol Davila’ University of Medicine and Pharmacy, RO-050474 Bucharest, Romania
Octavian Călinescu and Klaus Fendler


Recent studies performed on a series of Na+/H+ exchangers have led us to postulate a general mechanism for Na+/H+ exchange in the monovalent cation/proton antiporter superfamily. This simple mechanism employs a single binding site for which both substrates compete. The developed kinetic model is self-regulatory, ensuring down-regulation of transport activity at extreme pH, and elegantly explains the pH-dependent activity of Na+/H+ exchangers. The mechanism was experimentally verified and shown to describe both electrogenic and electroneutral exchangers. Using a small number of parameters, exchanger activity can be modeled under different conditions, providing insights into the physiological role of Na+/H+ exchangers.

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