Characterization and Three-Dimensional Structure Determination of ψ-Conotoxin Piiif , a Novel Noncompetitive Antagonist of Nicotinic Acetylcholine Receptors
| Autor: | Chris M. Ireland, Richard B. Jacobsen, Ryan M. Van Wagoner, Baldomero M. Olivera |
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| Rok vydání: | 2003 |
| Předmět: |
Models
Molecular Peptide Biosynthesis Protein Folding Magnetic Resonance Spectroscopy Protein Conformation Stereochemistry Recombinant Fusion Proteins Molecular Sequence Data Nicotinic Antagonists Receptors Nicotinic Torpedo complex mixtures Biochemistry Mass Spectrometry omega-Conotoxins law.invention Conus purpurascens Inhibitory Concentration 50 Xenopus laevis Ganglion type nicotinic receptor law Animals Amino Acid Sequence Disulfides Conotoxin Chromatography High Pressure Liquid Acetylcholine receptor biology Chemistry Stereoisomerism biology.organism_classification Protein Structure Tertiary Electrophysiology Nicotinic agonist Mollusca Oocytes Alpha-4 beta-2 nicotinic receptor Peptides Cys-loop receptors |
| Zdroj: | Biochemistry. 42:6353-6362 |
| ISSN: | 1520-4995 0006-2960 |
| DOI: | 10.1021/bi0272757 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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