The Sodium World

Abstract

The progress made in bioenergetic studies in the last few years has stimulated the interest in the role of Na⁺ ions. The dogma, assuming H⁺ as the coupling ion in all the energy-transducing membranes, with the only exception being the animal outer cell membrane, proved to be shaken. It was found that the role of Na⁺ is not restricted to Δ$\bar \mu$H buffering. In some forms of life, Na⁺ was shown to be directly involved in energy transductions, performing the function earlier ascribed to H⁺. The significant taxonomic variety of species employing Na⁺ as the primary coupling ion points to the ubiquitous distribution of this novel type of membrane-linked energy transduction. An impression arises that besides the world based upon H⁺ energetics there is a rather extensive area which may be defined as a “sodium world”. In this chapter, observations related to this new aspect of membrane bioenergetics will be considered.