title: Divalent cation effects on the Shaker K channel suggest a pentapeptide sequence as determinant of functional surface charge density.
abstract: 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.
authors.affiliation: Nobel Institute for Neurophysiology, Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: F
authors.initials: F
authors.lastname: Elinder
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
authors.forename: P
authors.initials: P
authors.lastname: Arhem
mesh_terms: D000818:Animals; D002412:Cations; D004594:Electrophysiology; D009842:Oligopeptides / Q000502:physiology*; D009865:Oocytes; D015221:Potassium Channels / Q000737:chemistry / Q000502:physiology*; D055672:Static Electricity; D013329:Structure-Activity Relationship; D014981:Xenopus
chemical_list: D002412:Cations; D009842:Oligopeptides; D015221:Potassium Channels