Effects of Oligomycin on Transient Currents Carried by Na+ Translocation of Bufo Na+/K+-ATPase Expressed in Xenopus Oocytes

Effects of Oligomycin on Transient Currents Carried by Na+ Translocation of Bufo Na+/K+-ATPase... Na+/K+-ATPase (NKA) exports 3Na+ and imports 2K+ at the expense of the hydrolysis of 1ATP under physiological conditions. In the absence of K+, it can mediate electroneutral Na+/Na+ exchange. In the electroneutral Na+/Na+ exchange mode, NKA produces a transient current containing fast, medium and slow components in response to a sudden voltage step. These three components of the transient current demonstrate the sequential release of Na+ ions from three binding sites. Our data from oocytes provide further experimental support for the existence of these components. Oligomycin is an NKA inhibitor that favors the 2Na+-occluded state without affecting the conformational state of the NKA. We studied the effects of oligomycin on both K+-activated currents and transient currents in wild-type Bufo NKA and a mutant form of Bufo NKA, NKA: G813A. Oligomycin blocked almost all of the K+-activated current, although the three components of the transient current showed different sensitivities to oligomycin. The oligomycin-inhibited charge movement measured using a P/4 protocol had a rate coefficient similar to the medium transient component. The fast component of the transient current elicited by a short voltage step also showed sensitivity to oligomycin. However, the slow component was not totally inhibited by oligomycin. Our results indicate that the second and third sodium ions might be released to the extracellular medium by a mechanism that is not shared by the first sodium ion. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Effects of Oligomycin on Transient Currents Carried by Na+ Translocation of Bufo Na+/K+-ATPase Expressed in Xenopus Oocytes

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Publisher
Springer-Verlag
Copyright
Copyright © 2011 by Springer Science+Business Media, LLC
Subject
Life Sciences; Human Physiology; Biochemistry, general
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232-011-9390-6
Publisher site
See Article on Publisher Site

Abstract

Na+/K+-ATPase (NKA) exports 3Na+ and imports 2K+ at the expense of the hydrolysis of 1ATP under physiological conditions. In the absence of K+, it can mediate electroneutral Na+/Na+ exchange. In the electroneutral Na+/Na+ exchange mode, NKA produces a transient current containing fast, medium and slow components in response to a sudden voltage step. These three components of the transient current demonstrate the sequential release of Na+ ions from three binding sites. Our data from oocytes provide further experimental support for the existence of these components. Oligomycin is an NKA inhibitor that favors the 2Na+-occluded state without affecting the conformational state of the NKA. We studied the effects of oligomycin on both K+-activated currents and transient currents in wild-type Bufo NKA and a mutant form of Bufo NKA, NKA: G813A. Oligomycin blocked almost all of the K+-activated current, although the three components of the transient current showed different sensitivities to oligomycin. The oligomycin-inhibited charge movement measured using a P/4 protocol had a rate coefficient similar to the medium transient component. The fast component of the transient current elicited by a short voltage step also showed sensitivity to oligomycin. However, the slow component was not totally inhibited by oligomycin. Our results indicate that the second and third sodium ions might be released to the extracellular medium by a mechanism that is not shared by the first sodium ion.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Aug 30, 2011

References

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