A peptide from the Drosophila Shaker K+ channel inhibits a voltage-gated K+ channel in basolateral membranes of Necturus enterocytes.

A synthetic peptide composed of the first 22 amino acid residues of the Drosophila Shaker K+ channel inhibits a voltage-gated K+ channel in basolateral membrane vesicles from Necturus enterocytes reconstituted in planar phospholipid bilayers when added to the solution bathing the inner surface of this channel but not when added to the solution bathing its outer surface. A modified peptide in which the leucine in the 7 position is replaced with phenylalanine is also an effective inhibitor, but replacement of the leucine-7 with lysine or glutamate, or digestion with trypsin, renders the peptide ineffective; replacement of the leucine-7 with glycine markedly reduces but does not abolish the effectiveness of the peptide as an inhibitor. These results are analogous to those reported for the Shaker K+ channel +ADHoshi, T., Zagotta, W.N. & Aldrich, R.W. (1990) Science 250, 533-538; and Zagotta, W.N., Hoshi, T. & Aldrich, R.W. (1990) Science 250, 568-571.+BD and suggest that the molecular anatomy of the receptor at the inner face of the Necturus K+ channel with which the peptide interacts to bring about inhibition of that channel may be similar to that of the Shaker K+ channel.