Single amino acid substitutions in kappa-conotoxin PVIIA disrupt interaction with the Shaker K+ channel

K-Conotoxin PVILA (kappa-PVIIA), a 27-amino acid peptide with three disulfi de cross-links, isolated from the venom of Conus purpurascens, is the first conopeptide shown to inhibit the Shaker K+ channel (Terlau, H., Shon, K., Grilley, M., Stocker, Ri., Stuhmer, W., and Olivera, B. M. (1996) Nature 38 1, 148-151). Recently, two groups independently determined the solution str ucture for kappa-PVIIA using NMR; although the structures reported were sim ilar, two mutually exclusive models for the interaction of the peptide with the Shaker channel were proposed. We carried out a structure/function anal ysis of kappa-PVIIA, with alanine substitutions for all amino acids postula ted to be key residues by both groups. Our data are consistent with the cri tical dyad model developed by Menez and co-workers (Dauplais, M., Lecoq, A. , Song, J., Cotton, J., Jamin, N., Gilquin, B., Roumestand, C., Vita, C., d e Medeiros, C., Rowan, E. G., Harvey, A. L., and Menez, A. (1997) J. Biol. Chem. 272, 4802-4809) for polypeptide antagonists of KC channels. In the ca se of kappa-PVIIA, Lys(7) and Phe(9) are essential for activity as predicte d by Savarin et al. (Savarin, P., Guenneugues, M., Gilquin, B., Lamthanh, H ., Gasparini, S., Zinn-Justin, S., and Menez, A. (1998) Biochemistry 37, 54 07-5416); these workers also correctly predicted an important role for Lys( 25). Thus, although K-conotoxin PVIIA has no obvious sequence homology to p olypeptide toxins from other venomous animals that interact with voltage-ga ted K+ channels, there may be convergent functional features in diverse KC channel polypeptide antagonists.