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J Membr Biol September 15, 1998; 165 (2): 183-9.

Divalent cation effects on the Shaker K channel suggest a pentapeptide sequence as determinant of functional surface charge density.

Elinder F , Liu Y , Arhem P .

The effects of the divalent cations strontium and magnesium on Shaker K channels expressed in Xenopus oocytes were investigated with a two-electrode voltage-clamp technique. 20 mM of the divalent cation shifted activation (conductance vs. potential), steady-state inactivation and inactivation time constant vs. potential curves 10-11 mV along the potential axis. The results were interpreted in terms of the surface charge theory, and the surface charge density was estimated to be -0.27 e nm-2. A comparison of primary structure data and experimental data from the present and previous studies suggests that the first five residues on the extracellular loop between transmembrane segment 5 and the pore region constitutes the functional surface charges. The results further suggest that the surface charge density plays an important role in controlling the activation voltage range.

PubMed ID: 9745006
Article link: J Membr Biol