MOLECULAR-IDENTIFICATION OF SQKV1A - A CANDIDATE FOR THE DELAYED RECTIFIER K-CHANNEL IN SQUID GIANT-AXON

We have cloned the cDNA for a squid Kvl potassium channel (SqKv1A). Sq Kv1A mRNA is selectively expressed in giant fiber lobe (GFL) neurons, the somata of the giant axons. Western blots detect two forms of SqKv1 A in both GFL neuron and giant axon samples. Functional properties of SqKv1A currents expressed in Xenopus oocytes are very similar to macro scopic currents in GFL neurons and giant axons. Macroscopic K currents in GFL neuron cell bodies, giant axons, and in Xenopus oocytes expres sing SqKv1A, activate rapidly and inactivate incompletely over a time course of several hundred ms. Oocytes injected With SqKv1A cRNA expres s channels of two conductance classes, estimated to be 13 and 20 pS in an internal solution containing 470 mM K. SqKv1A is thus a good candi date for the ''20 pS'' K channel that accounts for the majority of rap idly activating K conductance in both GFL neuron cell bodies and the g iant axon.