COMPLETELY FUNCTIONAL DOUBLE-BARRELED CHLORIDE CHANNEL EXPRESSED FROM A SINGLE TORPEDO CDNA

We have performed an electrophysiological analysis of the recently cloned Torpedo marmorata Cl- channel. Functional expression of Cl- channels in oocytes of Xenopus laevis previously injected with cRNA yielded an outward-rectifying current activated by hyperpolarization. Replacement of Cl- with other anions significantly reduced or inhibited the current. Single-channel recordings from cell-attached patches exhibited burst-like Cl- channel activity with rapid fluctuations between three equally spaced substates (0 pS, 9 pS, and 18 pS). The properties of the cloned Cl- channel were almost identical to those of the reconstituted native T. california Cl- channel and were in full agreement with the predictions of the double-barreled channel model [Hanke, W. & Miller, C. (1983) J. Gen. Physiol. 82, 25-45]. Our results imply that the cloned cDNA codes for the completely functional Torpedo electroplax Cl- channel.