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The dynamic relationships between the three events that release individual Na(+) ions from the Na(+)/K(+)-ATPase

Na(+)/K(+) pumps move net charge through the cell membrane by mediating unequal exchange of intracellular Na(+) and extracellular K(+). Most charge moves during transitions that release Na(+) to the cell exterior. When pumps are constrained to bind and release only Na(+), a membrane voltage-step red...

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Detalles Bibliográficos
Autores principales: Gadsby, David C., Bezanilla, Francisco, Rakowski, Robert F., De Weer, Paul, Holmgren, Miguel
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Nature Pub. Group 2012
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3293407/
https://www.ncbi.nlm.nih.gov/pubmed/22334072
http://dx.doi.org/10.1038/ncomms1673
Descripción
Sumario:Na(+)/K(+) pumps move net charge through the cell membrane by mediating unequal exchange of intracellular Na(+) and extracellular K(+). Most charge moves during transitions that release Na(+) to the cell exterior. When pumps are constrained to bind and release only Na(+), a membrane voltage-step redistributes pumps among conformations with zero, one, two or three bound Na(+), thereby transiently generating current. By applying rapid voltage steps to squid giant axons, we previously identified three components in such transient currents, with distinct relaxation speeds: fast (which nearly parallels the voltage-jump time course), medium speed (τ(m)=0.2–0.5 ms) and slow (τ(s)=1–10 ms). Here we show that these three components are tightly correlated, both in their magnitudes and in the time courses of their changes. The correlations reveal the dynamics of the conformational rearrangements that release three Na(+) to the exterior (or sequester them into their binding sites) one at a time, in an obligatorily sequential manner.