Cation transport systems in mitochondria: Na+ and K+ uniports and exchangers.
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 Ca(2+)-extruding mechanism that permits the mitochondrion to regulate matrix [Ca2+] by balancing Ca2+ efflux against influx on the Ca(2+)-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.
Brierley
G P
GP
Department of Medical Biochemistry, Ohio State University, Columbus 43210.
Baysal
K
K
Jung
D W
DW
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002414:Cations, Monovalent / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*
D002352:Carrier Proteins; D002414:Cations, Monovalent; D019831:Sodium-Calcium Exchanger; D017923:Sodium-Hydrogen Exchangers; D012964:Sodium; D011188:Potassium