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Original Article

^a Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York 14642
Department of Pharmacology and Physiology, Box 711, University of Rochester Medical Center, Rochester, NY 14642.(716) 273-2652

ted_begenisich{at}URMC.rochester.edu

We have examined the interaction between TEA and K⁺ ions in the pore of Shaker potassium channels. We found that the ability of external TEA to antagonize block of Shaker channels by internal TEA depended on internal K⁺ ions. In contrast, this antagonism was independent of external K⁺ concentrations between 0.2 and 40 mM. The external TEA antagonism of internal TEA block increased linearly with the concentration of internal K⁺ ions. In addition, block by external TEA was significantly enhanced by increases in the internal K⁺ concentration. These results suggested that external TEA ions do not directly antagonize internal TEA, but rather promote increased occupancy of an internal K⁺ site by inhibiting the emptying of that site to the external side of the pore. We found this mechanism to be quantitatively consistent with the results and revealed an intrinsic affinity of the site for K⁺ ions near 65 mM located 7% into the membrane electric field from the internal end of the pore. We also found that the voltage dependence of block by internal TEA was influenced by internal K⁺ ions. The TEA site (at 0 internal K⁺) appeared to sense 5% of the field from the internal end of the pore (essentially colocalized with the internal K⁺ site). These results lead to a refined picture of the number and location of ion binding sites at the inner end of the pore in Shaker K channels.

Key Words: ion channels • ion permeation • voltage-clamp • tetraethylammonium

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This article has been cited by other articles:

				F. Gomez-Lagunas Na+ Interaction with the Pore of Shaker B K+ Channels: Zero and Low K+ Conditions J. Gen. Physiol., December 1, 2001; 118(6): 639 - 648. [Abstract] [Full Text] [PDF]

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