Cation transport systems in mitochondria: Na+ and K+ uniports and exchangers |
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Authors: | Gerald P. Brierley Kemal Baysal Dennis W. Jung |
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Affiliation: | (1) Department of Medical Biochemistry, The Ohio State University, 43210 Columbus, Ohio |
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Abstract: | It is now well established that mitochondria contain three antiporters that transport monovalent cations. A latent, allosterically regulated K+/H+ antiport appears to serve as a cation-extruding device that helps maintain mitochondrial volume homeostasis. An apparently unregulated Na+/H+ antiport keeps matrix [Na+] low and the Na+-gradient equal to the H+-gradient. A Na+/Ca2+ antiport provides a Ca2+-extruding mechanism that permits the mitochondrion to regulate matrix [Ca2+] by balancing Ca2+ efflux against influx on the Ca2+-uniport. All three antiports have well-defined physiological roles and their molecular properties and regulatory features are now being determined. Mitochondria also contain monovalent cation uniports, such as the recently described ATP- and glibenclamide-sensitive K+ channel and ruthenium red-sensitive uniports for Na+ and K+. A physiological role of such uniports has not been established and their properties are just beginning to be defined. |
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