title: Orientation independence of single-vacancy and single-ion permeability ratios.
abstract: Single-vacancy models have been proposed as open channel permeation mechanisms for K+ channels. Single-ion models have been used to describe permeation through Na+ channels. This paper demonstrates that these models have a distinctive symmetry property. Their permeability ratios, measured under biionic conditions, are independent of channel orientation when the reversal potential is zero. This symmetry is a property of general m-site single-vacancy channels, m-site shaking-stack channels, as well as m-site single-ion channels. An experimental finding that the permeability ratios of a channel did not have this symmetry would provide evidence that a single-vacancy or single-ion model is an incorrect or incomplete description of permeation.
authors.affiliation: Department of Pure and Applied Mathematics, Washington State University, Pullman 99164, USA.
authors.forename: P
authors.initials: P
authors.lastname: McGill
authors.forename: M F
authors.initials: MF
authors.lastname: Schumaker
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology / Q000502:physiology; D015640:Ion Channel Gating; D007700:Kinetics; D008433:Mathematics; D008954:Models, Biological; D010539:Permeability; D015221:Potassium Channels / Q000502:physiology*
chemical_list: D015221:Potassium Channels; D002118:Calcium