Recent Studies on the Energy Profiles Underlying Permeation and Ion-Selectivity of the Gramicidin and Acetylcholine Receptor Channels

摘要: An unambiguous understanding of ion permeation, selectivity, and their relation to molecular structure function requires detailed information about the energy profiles encountered by ions during transport [15,25]. Here, we use Eyring rate theory approximations [19] develop simplified models for monovalent crossing gramicidin A [17,28] or acetylcholine receptor (AChR) channels [5, 34]. The are assessed fitting simple barrier open-channel current — voltage (I-V) relations obtained over a wide range symmetrical, single electrolyte concentrations. First describe I-V behavior Li, Na, K, Rb, Cs in channel using three-barrier, four-site (3B4S) model [58]. particular 3B4S″ variant [58] this describes electrical data well [16] is consistent with accepted tertiary proposed [61] from known primary sequence [59]. Then, initial Na [11] (J. A. Dani G. Eisenman, preparation) AChR described terms two-barrier, one-site (2B1S) models. Some indadequacies classical 2B1S [1, 30, 44, 45] removed allowing outer site have width. studies presented here represent start our exploration possible than can account data. We hope that they will give ultimately be matched structural [13, 22, 38, 53] based on sequences AChR’s subunits [6, 9,13, 51–53]. Eventually, as both permeation more clearly understood, integrated into overall AChR.