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Electrogenicity of the sodium transport pathway in the Na,K-ATPase probed by charge-pulse experiments

Electrogenicity of the sodium transport pathway in the Na,K-ATPase probed by charge-pulse experiments

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WUDDEL, Ingo, Hans-Jürgen APELL, 1995. Electrogenicity of the sodium transport pathway in the Na,K-ATPase probed by charge-pulse experiments. In: Biophysical Journal. 69(3), pp. 909-921. ISSN 0006-3495

@article{Wuddel1995Elect-6756, title={Electrogenicity of the sodium transport pathway in the Na,K-ATPase probed by charge-pulse experiments}, year={1995}, doi={10.1016/S0006-3495(95)79965-9}, number={3}, volume={69}, issn={0006-3495}, journal={Biophysical Journal}, pages={909--921}, author={Wuddel, Ingo and Apell, Hans-Jürgen} }

2011-03-24T17:28:57Z deposit-license eng Electrogenicity of the sodium transport pathway in the Na,K-ATPase probed by charge-pulse experiments application/pdf A charge-pulse technique was designed to measure charge movements in the Na-transport mode of the Na,K-ATPase in membrane fragments adsorbed to a planar lipid bilayer with high time resolution. 1) Na+ transport was measured as a function of membrane potential, and 2) voltage-dependent extracellular ion binding and release were analyzed as a function of Na+ concentration and membrane potential. The results could be fitted and explained on the basis of a Post-Albers cycle by simulations with a mathematical model. The minimal reaction sequence explaining the electrogenicity of the pump consists of the following steps: (Na3)E1-P P-E2(Na3) P-E2(Na2) P-E2(Na) P-E2. The conformational change, E1 to E2, is electrogenic (beta 0 < or = 0.1) and the rate-limiting step of forward Na+ transport with a rate constant of 25 s-1 (T = 20 degrees C). The first ion release step, P-E2(Na3) P-E2(Na2), is the major charge translocating process (delta 0 = 0.65). It is probably accompanied by a protein relaxation in which the access structure between aqueous phase and binding site reduces the dielectric distance. The release of the subsequent Na+ ions has a significantly lower dielectric coefficient (delta1 = delta 2 = 0.2). Compared with other partial reactions, the ion release rates are fast (1400 s-1, 700 s-1, and 4000 s-1). On the basis of these findings, a refined electrostatic model of the transport cycle is proposed. Wuddel, Ingo Apell, Hans-Jürgen Wuddel, Ingo First publ. in: Biophysical Journal 69 (1995), pp. 909-921 Apell, Hans-Jürgen 2011-03-24T17:28:57Z 1995

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