Single potassium channels with delayed rectifier behavior from lobster axon membranes.
Single-channel potassium currents from lobster axon membranes were studied in planar bilayers made from monolayers. Channel-opening events are grouped by time, forming bursts with an average duration of 4.5 ms. The mean open time at 0 mV is 1.8 ms. The frequency of bursts is voltage dependent, increasing e-fold per 12-16 mV. At sufficiently high positive voltages, channels inactivate. Measured from reversal potentials, channels discriminate against Na+ by a permeability ratio PNa/PK of 1:30. The channel is blocked by tetraethylammonium and nonyltrimethylammonium in a voltage-dependent manner and at concentrations similar to those used in whole-axon experiments. Voltage-dependent block by Cs+ suggests that more than one ion may occupy the channel simultaneously. The kinetics and selectivity of this channel suggest that purified axolemma contains active K+ channels that are likely to participate in delayed rectification in the lobster axon membrane.
D000818:Animals; D001369:Axons / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology; D004553:Electric Conductivity; D007473:Ion Channels / Q000502:physiology*; D007700:Kinetics; D008051:Lipid Bilayers; D008968:Molecular Conformation; D008121:Nephropidae; D011188:Potassium / Q000378:metabolism*
D007473:Ion Channels; D008051:Lipid Bilayers; D011188:Potassium