Kinetic comparison of heart and kidney Na+,K+-ATPases

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GARCIA, Alvaro, Helge H. RASMUSSEN, Hans-Jürgen APELL, Ronald J. CLARKE, 2012. Kinetic comparison of heart and kidney Na+,K+-ATPases. In: Biophysical Journal. 103(4), pp. 677-688. ISSN 0006-3495. eISSN 1542-0086. Available under: doi: 10.1016/j.bpj.2012.07.032

@article{Garcia2012-08-22Kinet-21324, title={Kinetic comparison of heart and kidney Na+,K+-ATPases}, year={2012}, doi={10.1016/j.bpj.2012.07.032}, number={4}, volume={103}, issn={0006-3495}, journal={Biophysical Journal}, pages={677--688}, author={Garcia, Alvaro and Rasmussen, Helge H. and Apell, Hans-Jürgen and Clarke, Ronald J.} }

2013-02-08T11:27:53Z Biophysical Journal ; 103 (2012), 4. - S. 677-688 Apell, Hans-Jürgen Kinetic comparison of heart and kidney Na<sup>+</sup>,K<sup>+</sup>-ATPases Apell, Hans-Jürgen 2012-08-22 Most kinetic measurements of the partial reactions of Na(+),K(+)-ATPase have been conducted on enzyme from mammalian kidney. Here we present a kinetic model that is based on the available equilibrium and kinetic parameters of purified kidney enzyme, and allows predictions of its steady-state turnover and pump current in intact cells as a function of ion and ATP concentrations and the membrane voltage. Using this model, we calculated the expected dependence of the pump current on voltage and extracellular Na(+) concentration. The simulations indicate a lower voltage dependence at negative potentials of the kidney enzyme in comparison with heart muscle Na(+),K(+)-ATPase, in agreement with experimental results. The voltage dependence is enhanced at high extracellular Na(+) concentrations. This effect can be explained by a voltage-dependent depopulation of extracellular K(+) ion binding sites on the E2P state and an increase in the proportion of enzyme in the E1P(Na(+))(3) state in the steady state. This causes a decrease in the effective rate constant for occlusion of K(+) by the E2P state and hence a drop in turnover. Around a membrane potential of zero, negligible voltage dependence is observed because the voltage-independent E2(K(+))(2) → E1 + 2K(+) transition is the major rate-determining step. Clarke, Ronald J. Garcia, Alvaro deposit-license 2013-02-08T11:27:53Z Rasmussen, Helge H. Clarke, Ronald J. Garcia, Alvaro Rasmussen, Helge H. eng

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