Cation Channels from Ciliary Membrane of Tetrahymena Reconstituted into Planar Lipid Bilayer. Comparison between the Channels from the Wild T. Thermophila and from Its Mutant Which Does Not Show Ciliary Reversal1

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Abstract
Cation channels in ciliary membrane vesicles from wild type Tetrahymena thermophila and from its mutant which does not show ciliary reversal or avoiding reaction were reconstituted into a planar lipid bilayer. Since the mutant does not produce the regenerative Ca2+ action potential, the mutation was expected to have occurred at the Ca-channel in the ciliary membrane. In the sample from the mutant, the channel most frequently observed was selective for cations over anions. The single channel conductance shows MichaelisMenten type dependency on the cation concentration. The maximum conductance and dissociation constants (in parenthesis) for K+, Mg2+ Ca2+ and Ba2+ were 371 PS (23.3 mM), 17 pS (0.49 mM), 18 pS (0.52 mM), and 25 pS (0.82 mM), respectively, when the anion was gluconate. The properties of the corresponding channel from the wild type are similar to those from the mutant. No essential difference was detected, which indicates that the predominant channel is not the putative Ca channel responsible for the avoiding reaction of Tetrahymena. Some other channels than the predominant channel were also observed.