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

Abstract

κ-Conotoxin PVIIA (κ-PVIIA), a 27-amino acid peptide with three disulfide 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, M., Stuhmer, W., and Olivera, B. M. (1996) Nature 381, 148-151). Recently, two groups independently determined the solution structure for κ-PVIIA using NMR; although the structures reported were similar, two mutually exclusive models for the interaction of the peptide with the Shaker channel were proposed. We carried out a structure/function analysis of κ-PVIIA, with alanine substitutions for all amino acids postulated to be key residues by both groups. Our data are consistent with the critical dyad model developed by Menez and co-workers (Dauplais, M., Lecoq, A., Song, J., Cotton, J., Jamin, N., Gilquin, B., Roumestand, C., Vita, C., de Medeiros, C., Rowan, E. G., Harvey, A. L., and Menez, A. (1997) J. Biol. Chem. 272, 4802-4809) for polypeptide antagonists of K+ channels. In the case of κ-PVIIA, Lys7 and Phe9 are essential for activity as predicted by Savarin et al. (Savarin, P., Guenneugues, M., Gilquin, B., Lamthanh, H., Gasparini, S., Zinn-Justin, S., and Menez, A. (1998) Biochemistry 37, 5407-5416); these workers also correctly predicted an important role for Lys25. Thus, although κ-conotoxin PVIIA has no obvious sequence homology to polypeptide toxins from other venomous animals that interact with voltage-gated K+ channels, there may be convergent functional features in diverse K+ channel polypeptide antagonists.