Details

Autor(en) / Beteiligte

• Balshaw, David M.
• Millette, Lauren A.
• Tepperman, Katherine
• Wallick, Earl T.

Titel

Combined Allosteric and Competitive Interaction between Extracellular Na + and K + During Ion Transport by the α 1, α 2, and α 3 Isoforms of the Na, K-ATPase

Ist Teil von

• Biophysical journal, 2000, Vol.79 (2), p.853-862

Ort / Verlag

Elsevier Inc

Erscheinungsjahr

2000

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• A combined allosteric and competitive model describes the interaction between extracellular Na + and Rb + during ion transport mediated by the Na, K-ATPase. The model was developed from experiments based on 86Rb uptake by whole cells transfected with rat isoforms of the enzyme. In the absence of Na +, only a single transport site for extracellular Rb + exists. After the occupation of the Na +-specific allosteric site, the Rb + transport pocket opens to allow occupation by an additional Rb + and the subsequent transport of the two Rb + ions into the cells. Na + can also directly compete with Rb + for binding to at least one of the transport sites. While the model derived here applies to each of the three rat isoforms of the Na, K-ATPase expressed in HeLa cells, subtle differences exist among the isoforms. The α 3* isoform has an increased intrinsic affinity for Rb + and a lower affinity for the allosteric Na + site than α 1 or α 2*. The stimulation of uptake observed according to the best-fit model is due to the displacement by Rb + of inhibitory Na + bound to the transport site.