BgK is a K+ channel-blocking toxin from the sea anemone Bunodosoma granulifera It is a 37-residue protein that adopts a novel fold, as determined by NMR and modeling. An alanine-scanning-based analysis revealed the functional importance of five residues, which include a critical lysine and an aromatic residue separated by 6.6 ± 1.0 Å. The same diad is found in the three known homologous toxins from sea anemones. More strikingly, a similar functional diad is present in all K+ channel-blocking toxins from scorpions, although these toxins adopt a distinct scaffold. Moreover, the functional diads of potassium channel-blocking toxins from sea anemone and scorpions superimpose in the three-dimensional structures. Therefore, toxins that have unrelated structures but similar functions possess conserved key functional residues, organized in an identical topology, suggesting a convergent functional evolution for these small proteins.
- animal toxins
- potassium channel-blocking toxins
Dauplais, M., Lecoq, A., Song, J. X., Cotton, J., Jamin, N., Gilquin, B., Rowan, E. G., & Vita, C. (1997). On the convergent evolution of animal toxins - conservation of a diad of functional residues in potassium channel-blocking toxins with unrelated structures. Journal of Biological Chemistry, 272(7), 4302-4309. https://doi.org/10.1074/jbc.272.7.4302