Delta-conotoxin structure/function through a cladistic analysis.
Delta-conotoxins are Conus peptides that inhibit inactivation of voltage-gated sodium channels. The suggestion that delta-conotoxins might be an essential component of the venoms of fish-hunting cone snails which rapidly immobilize their prey [Terlau, H., Shon, K., Grilley, M., Stocker, M., Stühmer, W., and Olivera, B. M. (1996) Nature 381, 148-151] has not been tested. On the basis of cDNA cloning, all of the fish-hunting Conus analyzed yielded at least one delta-conotoxin sequence. In addition, one delta-conotoxin isolated from the venom of Conus striatus had an amino acid sequence identical to that predicted from cDNA cloning. This new peptide exhibited properties of delta-conotoxins: it targeted sodium channels and potentiated action potentials by slowing channel inactivation. Homologous sequences of delta-conotoxins from two groups (clades) of related fish-hunting Conus species share consensus features but differ significantly from the two known delta-conotoxins from mollusc-hunting Conus venoms. Three large hydrophobic amino acids were conserved; analogues of the previously described delta-conotoxin PVIA with alanine substituted for the conserved amino acids F9 and I12 lost substantial biological activity. In contrast, both the T8A and K13A delta-conotoxin PVIA analogues, where substitutions were at nonconserved loci, proved to be biologically active. Taken together, our results indicate that a cladistic approach can identify amino acids critical for the activity of conotoxins and provide extensive information as to which amino acid substitutions can be made without significant functional consequences.
Bulaj
G
G
Department of Biology, University of Utah, Salt Lake City, Utah 84112, USA. bulaj@biology.utah.edu
DeLaCruz
R
R
Azimi-Zonooz
A
A
West
P
P
Watkins
M
M
Yoshikami
D
D
Olivera
B M
BM
D000200:Action Potentials; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D003001:Cloning, Molecular; D020916:Conotoxins / Q000737:chemistry* / Q000494:pharmacology; D017124:Conserved Sequence; D018076:DNA, Complementary; D004594:Electrophysiology; D015640:Ion Channel Gating / Q000187:drug effects; D051379:Mice; D008969:Molecular Sequence Data; D008978:Mollusk Venoms / Q000737:chemistry; D011894:Rana pipiens; D012584:Sciatic Nerve / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D026941:Sodium Channel Blockers; D015222:Sodium Channels / Q000187:drug effects; D013329:Structure-Activity Relationship
D020916:Conotoxins; D018076:DNA, Complementary; D008978:Mollusk Venoms; D026941:Sodium Channel Blockers; D015222:Sodium Channels; C089621:delta-conotoxin GmVIA; C093008:delta-conotoxin PVIA