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  Na+ currents generated by the purified Na+K+-ATPase on planar lipid membranes

Nagel, G., Fendler, K., Grell, E., & Bamberg, E. (1987). Na+ currents generated by the purified Na+K+-ATPase on planar lipid membranes. Biochimica et Biophysica Acta-Biomembranes, 901(2), 239-249. doi:10.1016/0005-2736(87)90120-9.

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 Creators:
Nagel, Georg1, Author           
Fendler, Klaus1, Author           
Grell, Ernst2, Author           
Bamberg, Ernst1, Author           
Affiliations:
1Transport Proteins Group, Max Planck Institute of Biophysics, Max Planck Society, ou_3273415              
2Molecular Biophysics Group, Max Planck Institute of Biophysics, Max Planck Society, ou_3264820              

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Free keywords: ATPase, (Na++K+); Pump current; Black lipid membrane; caged ATP; (Pig kidney)
 Abstract: Purified (Na++K+)-ATPase from pig kidney was attached to black lipid membranes and ATP-induced electric currents were measured as described previously by Fendler et al. ((1985) EMBO J. 4, 3079–3085). An ATP concentration jump was produced by an ultraviolet-light flash converting non-hydrolysable caged ATP to ATP. In the presence of Na+ and Mg2+ this resulted in a transient current signal. The pump current was not only ATP dependent, but also was influenced by the ATP/caged ATP ratio. It was concluded that caged ATP binds to the enzyme (and hence inhibits the signal) with a Ki of approx. 30 μM, which was confirmed by enzymatic activity studies. An ATP affinity of approx. 2 μM was determined. The addition of the protonophore 1799 and the Me+/H+ exchanger monensin made the bilayer conductive leading to a stationary pump current. The stationary current was strongly increased by the addition of K+ with a K05 of 700 μM. Even in the absence of K+ a stationary current could be measured, which showed two Na+-affinities: a high-affinity (K05 <1mM) and a low-affinity (K05 <2mM). In order to explain the sustained electrogenic Na+ transport during the Na+-ATPase activity, it is proposed, that Na+ can replace K+ in dephophorylating the enzyme, but binds about 1000-times weaker than K+. The ATP requirement of the Na+-ATPase was the same (K05 <2 μM) with regard to the peak currents and the stationary currents. However, for the the stationary currents required more ATP. The results are discussed on the basis of the Albers-Post scheme.

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Language(s): eng - English
 Dates: 1987-01-302003-01-281987-07-23
 Publication Status: Published in print
 Pages: 11
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1016/0005-2736(87)90120-9
PMID: 3038187
 Degree: -

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Title: Biochimica et Biophysica Acta-Biomembranes
Source Genre: Journal
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Publ. Info: Amsterdam : Elsevier
Pages: - Volume / Issue: 901 (2) Sequence Number: - Start / End Page: 239 - 249 Identifier: ISSN: 0005-2736
CoNE: https://pure.mpg.de/cone/journals/resource/954926938702