Repulsion between tetraethylammonium ions in cloned voltage-gated potassium channels.
Tetraethylammonium ion (TEA+) blocks voltage-gated K+ channels by acting at two sites located at opposite ends of the aqueous pore. This allowed us to test two predictions made by models of ion permeation, namely that K+ channels can be simultaneously occupied by multiple ions and that the ions repel each other. We show that externally applied TEA+ antagonize block by internal TEA+ and vice versa. The antagonism is less than predicted for competitive binding, hence TEA+ may occupy both sites simultaneously. External TEA+ and internal TEA+ reduce each others affinity 4- to 5-fold. In addition, K+ antagonizes block by TEA+ at the opposite side of the membrane, and external TEA+ antagonizes is block by internal Ba2+. The antagonism between ions applied at opposite sides of the membrane may be common to all cations binding to K+ channels.
Newland
C F
CF
Department of Physiology and Biophysics, University of Washington, Seattle 98195.
Adelman
J P
JP
Tempel
B L
BL
Almers
W
W
D000818:Animals; D001464:Barium / Q000494:pharmacology; D001667:Binding, Competitive; D002412:Cations; D004594:Electrophysiology; D005260:Female; D009865:Oocytes / Q000502:physiology; D011188:Potassium / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology*; D014162:Transfection; D014982:Xenopus laevis
D002412:Cations; D015221:Potassium Channels; D012333:RNA, Messenger; D013757:Tetraethylammonium Compounds; D001464:Barium; D019789:Tetraethylammonium; D011188:Potassium