Open AccessKinetic contribution to extracellular Na + /K + selectivity in the Na + /K + pump
Author(s) -
Vleeskens Elizabeth,
Clarke Ronald J.
Publication year - 2018
Publication title -
febs open bio
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.718
H-Index - 31
ISSN - 2211-5463
DOI - 10.1002/2211-5463.12418
Subject(s) - selectivity , extracellular , chemistry , sodium , ion transporter , ion , potassium , membrane transport , extracellular fluid , biophysics , membrane , biochemistry , biology , catalysis , organic chemistry
The sodium potassium pump (Na + ,K + ‐ATPase) shows a high selectivity for K + over Na + binding from the extracellular medium. To understand the K + selectivity in the presence of a high concentration of competing Na + ions requires consideration of more than just ion binding affinities. Here, equilibrium‐based calculations of the extracellular occupation of the Na + ,K + ‐ATPase transport sites by Na + and K + are compared to fluxes through Na + and K + transport pathways. The results show that, under physiological conditions, there is a 332‐fold selectivity for pumping of K + from the extracellular medium into the cytoplasm relative to Na + , whereas equilibrium calculations alone predict only a 7.5‐fold selectivity for K + . Thus, kinetic effects make a major contribution to the determination of extracellular K + selectivity.