D. Taglicht is the first author of a 1993 measurement of the transport stoichiometry of NhaA, an antiporter from Escherichia coli. Purified NhaA was reconstituted into sodium-loaded proteoliposomes, allowing transport to be studied in a defined membrane preparation.[ref]
Two approaches converged on two protons exchanged for each sodium ion over the tested pH interval –. One compared opposing ion fluxes; the other related the membrane potential to imposed concentration gradients under coupling and equilibrium assumptions.[ref]
The ratio explains the word electrogenic: moving two singly positive ions one way and one singly positive ion the other transfers a net unit of positive charge per completed exchange cycle. It also separates a transporter's rate from its stoichiometry: faster exchange need not mean a different number of ions per cycle.
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