Activation of Na+ and K+ pumping modes of (Na,K)-ATPase by an oscillating electric field.
Serpersu and Tsong (Sepersu, E. H., and Tsong, T. Y. (1983) J. Membr. Biol. 74, 191-201; (1984) J. Biol. Chem. 259, 7155-7162) reported activation of a K+ pumping mode of (Na,K)-ATPase by an oscillating electric field (20 V/cm, 1.0 kHz). Their attempts to activate Na+ pumping at the same frequency were unsuccessful. We report here activation of a Na+ pumping mode with an oscillating electric field of the same strength as used previously (20 V/cm) but at a much higher frequency (1.0 MHz). At 3.5 degrees C and the optimal amplitude and frequency, the field-induced, ouabain-sensitive (0.2 mM ouabain incubated for 30 min) Rb+ influx ranged between 10 and 20 amol/red blood cell/h, and the corresponding Na+ efflux ranged between 15 and 30 amol/red blood cell/h, varying with the source of the erythrocytes. No Rb+ efflux nor Na+ influx was stimulated by the applied field in the frequency range 1 Hz to 10 MHz. These results indicate that only those transport modes that require ATP splitting under the physiological condition were affected by the applied electric fields, although the field-stimulated Rb+ influx and Na+ efflux did not depend on the cellular ATP concentration in the range 5 to 800 microM. Computer simulation of a four-state enzyme electroconformationally coupled to an alternating electric field (Tsong, T. Y., and Astumian, R. D. (1986) Bioelectrochem. Bioenerg. 15, 457-476; Tsong, T. Y. (1990) Annu. Rev. Biophys. Biophys. Chem. 19, 83-106) reproduced the main features of the above results.
Liu
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DS
Department of Biochemistry, University of Minnesota College of Biological Sciences, St. Paul 55108.
Astumian
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RD
Tsong
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D000255:Adenosine Triphosphate / Q000097:blood; D001693:Biological Transport, Active; D004558:Electric Stimulation / Q000379:methods; D004912:Erythrocytes / Q000201:enzymology / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008433:Mathematics; D008962:Models, Theoretical; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000097:blood*; D012413:Rubidium / Q000097:blood; D012964:Sodium / Q000097:blood*; D000254:Sodium-Potassium-Exchanging ATPase / Q000097:blood*; D013050:Spectrometry, Fluorescence
D010042:Ouabain; D000255:Adenosine Triphosphate; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium; D011188:Potassium