Molecular identification of SqKv1A: A candidate for the delayed rectifier K channel in squid giant axon

Abstract

We have cloned the cDNA for a squid Kv1 potassium channel (SqKv 1 A). SqKv 1 A mRNA is selectively expressed in giant fiber lobe (GFL) neurons, the somata of the giant axons. Western blots detect two forms of SqKv 1 A in both GFL, neuron and giant axon samples. Functional properties of SqKv 1 A currents expressed in Xenopus oocytes are very similar to macroscopic currents in GFL neurons and giant axons. Macroscopic K currents in GFL neuron cell bodies, giant axons, and in Xenopus oocytes expressing SqKv 1 A, activate rapidly and inactive incompletely over a time course of several hundred ms. Oocytes injected with SqKv 1 A cRNA express channels of two conductance classes, estimated to be 13 and 20 pS in an internal solution containing 470 mM K, SqKv 1 A is thus a good candidate for the '20 pS' K channel that accounts for the majority of rapidly activating K conductance in both GFL neuron cell bodies and the giant axon.