Characterization of ion channels from Acetabularia plasma membrane in planar lipid bilayers.

摘要: Plasma membrane from Acetabularia acetabulum was prepared by aqueous-polymer two-phase partitioning and incorporated into planar 1-palmitoyl-2-oleoyl phosphatidylethanolamine bilayers stirring in the presence of a (cis:trans) 325:100 mM KCl gradient. Under these conditions five distinct K(+)-selective channels were observed which had unitary chord-conductances (determined between 30 mV either side reversal potential) frequencies incorporation (in parentheses) 1,600 pS (26%), 485 (21%), 259 (53%), 140 (37%) 27 (37%). Two Cl(-)-selective also observed, 8 48 present 21 16% bilayers, respectively. The voltage dependencies channel open probability (Po), open-state time constant (tau o) closed-state c) determined for 259, K+ channels. Po all three increased with increasingly positive potentials. Thus, since oriented their extracellular face adjacent to cis chamber, grounded, would exhibit outward rectification vivo. Changes effected modulation tau c channels, shortened as potentials became more positive, o positive. Extracellular (cis) concentration (and/or gradient across bilayer) affected shifting Po/membrane potential relationship direction change potassium potential. In this achieved largely changes c.