Abstract
CENTRAL to all formulations of the transport mechanism of the membrane Na-K pump should be the description of cation binding and release. The acceptance sites for transport by the pump, external sites for K and internal sites for Na, have been extensively studied, and linked to the activating sites of the associated Na,K-ATPase1. By contrast, little is known about the discharge sites of the pump, although proposed characteristics of these sites have vital roles in various transport and enzyme schemes, such as cyclical conversions of discharge sites for one cation into acceptance sites for the other. We have studied the apparent affinity for K at its intracellular discharge sites by measuring the rate of ATP synthesis as a function of the internal K concentration in resealed red blood cell ghosts, where the Na-K pump is driven in reverse by the downhill efflux of K and influx of Na: the observed K0.5 for internal K was 0.3 M.
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ROBINSON, J., HALL, E. & DUNHAM, P. Reversal of the Na-K pump and apparent affinity for intracellular potassium. Nature 269, 165–167 (1977). https://doi.org/10.1038/269165a0
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DOI: https://doi.org/10.1038/269165a0
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