Sequential Potassium Binding at the Extracellular Side of the Na,K-Pump

Bühler, R.; Apell, Hans-Jürgen

Sequential Potassium Binding at the Extracellular Side of the Na,K-Pump

Dateien

Sequential_Potassium_Binding.pdfGröße: 785.92 KBDownloads: 346

Datum

1995

Autor:innen

Bühler, R.

Apell, Hans-Jürgen

Open Access-Veröffentlichung

Open Access Green

Sammlungen

Biologie

Publikationstyp

Zeitschriftenartikel

Publikationsstatus

Published

Erschienen in

The Journal of Membrane Biology. 1995, 145(2), pp. 165-173. ISSN 0022-2631. eISSN 1432-1424. Available under: doi: 10.1007/BF00237374

Zusammenfassung

Ion binding at the extracellular face of the Na,K-ATPase is electrogenic and can be monitored by the styryl dye RH 421 in membrane fiagments containing a high density of the Na,K-pumps. The fluorescent probe is noncovalently bound to the membrane and responds to changes of the local electric field generated by binding or release of cations inside the protein. Due to the fact that K+ binding fiom the extracellular side is an electrogenic reaction, it is possible to detect the amount of ions bound to the pump as function of the aqueous concentration. The results are in contradiction to a second order reaction, i. e., a simultaneous binding of two K+ions. A mathematical model is presented to discuss the nature of the two step binding process. On the basis of this model the data allow a quantitatived istinction between binding of the first and the second K+ ion. The temperature dependence of ion binding has been investigated. At low temperatures the apparent dissociation constants differ significantly. In the temperature range above 20°C the resulting apparent dissociation constants for both K+ ions merge and have values between 0.2 and 0.3 mм, which is consistent with previous experiments. The activation energy for the half saturating concentration of K+ is 22 kJ/mol. Additional analysis of the titration curve of K+ binding to the state P - E2 by the Hill equation yields a Hill coefficientf,nHill, of 1.33, which is in agreement with previously published data.

Fachgebiet (DDC)

570 Biowissenschaften, Biologie

Schlagwörter

Na,K-ATPase, Potassium binding, Electrogenic transport, Cation binding site, Sequential binding, Activation energy

Zitieren

ISO 690

BÜHLER, R., Hans-Jürgen APELL, 1995. Sequential Potassium Binding at the Extracellular Side of the Na,K-Pump. In: The Journal of Membrane Biology. 1995, 145(2), pp. 165-173. ISSN 0022-2631. eISSN 1432-1424. Available under: doi: 10.1007/BF00237374

BibTex

@article{Buhler1995Seque-7076,
  year={1995},
  doi={10.1007/BF00237374},
  title={Sequential Potassium Binding at the Extracellular Side of the Na,K-Pump},
  number={2},
  volume={145},
  issn={0022-2631},
  journal={The Journal of Membrane Biology},
  pages={165--173},
  author={Bühler, R. and Apell, Hans-Jürgen}
}

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