Four cDNA clones from the Shaker locus of Drosophila induce kinetically distinct A-type potassium currents in Xenopus oocytes.

The Shaker gene encodes the A-channel of larval and pupal muscle, or one or more of its subunits. Alternative splicing produces messages for several different proteins; two mRNA species have previously been shown to induce the expression of A-currents in Xenopus oocytes. Two additional mRNAs have now been tested and found to produce A-currents in oocytes. The four currents differ in kinetics of inactivation, indicating that the Shaker products may contribute to kinetic diversity in A-channels of the fly and that sequences in both the amino- and carboxy-terminal regions are important for inactivation.