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Journal Article

Two-electrode voltage-clamp analysis of Na,K-ATPase asparagine 776 mutants

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Koenderink,  Jan B.
Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society;

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Geibel,  Sven
Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society;

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Grabsch,  Eva
Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society;

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Bamberg,  Ernst
Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society;

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Friedrich,  Thomas
Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society;

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Citation

Koenderink, J. B., Geibel, S., Grabsch, E., De Pont, J. J. H., Bamberg, E., & Friedrich, T. (2003). Two-electrode voltage-clamp analysis of Na,K-ATPase asparagine 776 mutants. Annals of the New York Academy of Sciences, 986, 150-154. doi:10.1111/j.1749-6632.2003.tb07152.x.


Cite as: https://hdl.handle.net/11858/00-001M-0000-0024-DBDC-6
Abstract
Steady-state and pre-steady-state currents of Asn776 mutants of Na,K-ATPase are presented. The stationary current generated by N776Q strongly depends on the membrane potential, but has a negative slope, opposite to that of the wild-type enzyme. The apparent rate constant of the reaction sequence E1P(Na+) <--> E2P + Na+ of this mutant is rather independent of the membrane potential and is at resting and depolarizing membrane potential higher than that of the wild-type enzyme. Thus, the voltage-dependent increase of the rate coefficient of the wild type that is associated with extracellular Na+ rebinding is almost absent in the N776Q mutant. These findings indicate that dislocating the carboxamide group of Asn776 decreases the affinity of sodium at its extracellular binding site.