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Block of K+ channels can be influenced by the ability of charged residues on the protein surface to accumulate cationic blocking ions to concentrations greater than those in bulk solution. We examined the ionic strength dependence of extracellular block of Shaker K+ channels by tetraethylammonium ions (TEA+) and by a trivalent quaternary ammonium ion,(More)
The effects of Ba2+, Mg2+, Ca2+ and Na+ as blocking ions were investigated in 90 and 10 mM extracellular K+ solutions on the cloned inward rectifying K+ channel Kir2.1 expressed in Xenopus oocytes. Some data were also obtained using another inward rectifying K+ channel Kir3.1/Kir3.4. The addition of Ba2+ caused a concentration-, voltage- and time-dependent(More)
Mechanisms and residues responsible for slow activation and Ba(2+) block of the cardiac muscarinic K(+) channel, Kir3.1/Kir3.4, were investigated using site-directed mutagenesis. Mutagenesis of negatively charged residues located throughout the pore of the channel (in H5, M2, and proximal C terminus) reduced or abolished slow activation. The strongest(More)
In spite of a generally well-conserved outer vestibule and pore structure, there is considerable diversity in the pharmacology of K channels. We have investigated the role of specific outer vestibule charged residues in the pharmacology of K channels using tetraethylammonium (TEA) and a trivalent TEA analog, gallamine. Similar to Shaker K channels,(More)
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