Characterization and Three-Dimensional Structure Determination of psi-Conotoxin Piiif, a Novel Noncompetitive Antagonist of Nicotinic Acetylcholine ReceptorsVan Wagoner, R.M., Ireland, C.M.
(2003) Biochemistry 42: 6353-6362
- PubMed: 12767216
- DOI: 10.1021/bi0272757
- PubMed Abstract:
- Three-dimensional Solution Structure of Conotoxin psi-PIIIE, an Acetylcholine Gated Ion Channel Antagonist
Mitchell, S.S.,Shon, K.J.,Foster, M.P.,Davis, D.R.,Olivera, B.M.,Ireland, C.M.
(1998) Biochemistry 37: 1215
- A Noncompetitive Peptide Inhibitor of the Nicotinic Acetylcholine Receptor from Conus purpurascens Venom
Shon, K.J.,Grilley, M.,Jacobsen, R.,Cartier, G.E.,Hopkins, C.,Gray, W.R.,Watkins, M.,Hillyard, D.R.,Rivier, J.,Torres, J.,Yoshikami, D.,Olivera, B.M.
(1997) Biochemistry 36: 9581
A novel inhibitor of nicotinic acetylcholine receptors (nAChRs), psi-conotoxin Piiif, was isolated from the venom of Conus purpurascens and found to have the sequence GOOCCLYGSCROFOGCYNALCCRK-NH2. The sequence is highly homologous to that of psi-cono ...
A novel inhibitor of nicotinic acetylcholine receptors (nAChRs), psi-conotoxin Piiif, was isolated from the venom of Conus purpurascens and found to have the sequence GOOCCLYGSCROFOGCYNALCCRK-NH2. The sequence is highly homologous to that of psi-conotoxin Piiie, a previously identified noncompetitive inhibitor of Torpedo electroplax nAChR, also isolated from C. purpurascens. Both psi-conotoxins block Torpedo and mouse nicotinic acetylcholine receptors (nAChRs), but psi-Piiif is less potent by a factor of 10(1)-10(2). A high-resolution structure of psi-Piiif was determined by NMR and molecular modeling calculations. Psi-Piiif analogues containing [(13)C]-labeled cysteine at selected positions were synthesized to resolve spectral overlap of Cys side chain proton signals. The structures are well-converged, with backbone atom position RMSDs of 0.21 A for the main body of the peptide between residues 4 and 22 and 0.47 A for all residues. The overall backbone conformation is closely similar to psi-Piiie, the main difference being in the degree of conformational disorder at the two termini. Psi-Piiie and psi-Piiif have similar locations of positive charge density, although psi-Piiif has a lower overall charge. One disulfide bridge of psi-Piiif appears to undergo dynamic conformational fluctuations based on both the model and on experimental observation. Chimeras in which the three intercysteine loops were swapped between psi-Piiie and psi-Piiif were tested for inhibitory activity against Torpedo nAChRs. The third loop, which contains no charged residues in either peptide, is the prime determinant of potency in these psi-conotoxins.
Department of Medicinal Chemistry, University of Utah, Salt Lake City, Utah 84112, USA.