RT Journal Article
SR Electronic
T1 Isolation and Structure-Activity of μ-Conotoxin TIIIA, A Potent Inhibitor of Tetrodotoxin-Sensitive Voltage-Gated Sodium Channels
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 676
OP 685
DO 10.1124/mol.106.028225
VO 71
IS 3
A1 Richard J. Lewis
A1 Christina I. Schroeder
A1 Jenny Ekberg
A1 Katherine J. Nielsen
A1 Marion Loughnan
A1 Linda Thomas
A1 Denise A. Adams
A1 Roger Drinkwater
A1 David J. Adams
A1 Paul F. Alewood
YR 2007
UL http://molpharm.aspetjournals.org/content/71/3/676.abstract
AB μ-Conotoxins are three-loop peptides produced by cone snails to inhibit voltage-gated sodium channels during prey capture. Using polymerase chain reaction techniques, we identified a gene sequence from the venom duct of Conus tulipa encoding a new μ-conotoxin-TIIIA (TIIIA). A 125I-TIIIA binding assay was established to isolate native TIIIA from the crude venom of Conus striatus. The isolated peptide had three post-translational modifications, including two hydroxyproline residues and C-terminal amidation, and <35% homology to other μ-conotoxins. TIIIA potently displaced [3H]saxitoxin and 125I-TIIIA from rat brain (Nav1.2) and skeletal muscle (Nav1.4) membranes. Alanine and glutamine scans of TIIIA revealed several residues, including Arg14, that were critical for high-affinity binding to tetrodotoxin (TTX)-sensitive Na+ channels. We were surprised to find that [E15A]TIIIA had a 10-fold higher affinity than TIIIA for TTX-sensitive sodium channels (IC50, 15 vs. 148 pM at rat brain membrane). TIIIA was selective for Nav1.2 and -1.4 over Nav1.3, -1.5, -1.7, and -1.8 expressed in Xenopus laevis oocytes and had no effect on rat dorsal root ganglion neuron Na+ current. 1H NMR studies revealed that TIIIA adopted a single conformation in solution that was similar to the major conformation described previously for μ-conotoxin PIIIA. TIIIA and analogs provide new biochemical probes as well as insights into the structure-activity of μ-conotoxins. The American Society for Pharmacology and Experimental Therapeutics