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Updated: Aug 18, 2026

Patch Clamp and Perfusion Techniques for Studying Ion Channels Expressed in Xenopus oocytes
Published on: January 11, 2011
Na+ block and permeation in a K+ channel of known structure
Crina M Nimigean1, Christopher Miller
1Department of Biochemistry, Howard Hughes Medical Institute, Brandeis University, Waltham, MA 02454, USA.
Abstract:
The effects of intracellular Na(+) were studied on K(+) and Rb(+) currents through single KcsA channels. At low voltage, Na(+) produces voltage-dependent block, which becomes relieved at high voltage by a "punchthrough" mechanism representing Na(+) escaping from its blocking site through the selectivity filter. The Na(+) blocking site is located in the wide, hydrated vestibule, and it displays unexpected selectivity for K(+) and Rb(+) against Na(+). The voltage dependence of Na(+) block reflects coordinated movements of the blocker with permeant ions in the selectivity filter.
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