Solution Structure of μ-Conotoxin PIIIA, a Preferential Inhibitor of Persistent Tetrodotoxin-sensitive Sodium Channels

• Published in: The Journal of biological chemistry Vol. 277; no. 30; pp. 27247 - 27255
• Main Authors: Nielsen, Katherine J., Watson, Michael, Adams, David J., Hammarström, Anna K., Gage, Peter W., Hill, Justine M., Craik, David J., Thomas, Linda, Adams, Denise, Alewood, Paul F., Lewis, Richard J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 26.07.2002
• Subjects: Amino Acid Sequence; Animals; Brain - drug effects; Brain - metabolism; Conotoxins - chemistry; Dose-Response Relationship, Drug; Electrophysiology; Hippocampus - metabolism; Humans; Inhibitory Concentration 50; Magnetic Resonance Spectroscopy; Marine; Models, Molecular; Molecular Sequence Data; Muscle, Skeletal - drug effects; Muscle, Skeletal - metabolism; Neurons - metabolism; Peptide Biosynthesis; Protein Conformation; Radioligand Assay; Rats; Sodium Channels - chemistry; Tetrodotoxin - pharmacology; Time Factors
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M201611200

μ-Conotoxins are peptide inhibitors of voltage-sensitive sodium channels (VSSCs). Synthetic forms of μ-conotoxins PIIIA and PIIIA-(2–22) were found to inhibit tetrodotoxin (TTX)-sensitive VSSC current but had little effect on TTX-resistant VSSC current in sensory ganglion neurons. In rat brain neurons, these peptides preferentially inhibited the persistent over the transient VSSC current. Radioligand binding assays revealed that PIIIA, PIIIA-(2–22), and μ-conotoxin GIIIB discriminated among TTX-sensitive VSSCs in rat brain, that these and GIIIC discriminated among the corresponding VSSCs in human brain, and GIIIA had low affinity for neuronal VSSCs. 1H NMR studies found that PIIIA adopts two conformations in solution due tocis/trans isomerization at hydroxyproline 8. The major trans conformation results in a three-dimensional structure that is significantly different from the previously identified conformation of μ-conotoxins GIIIA and GIIIB that selectively target TTX-sensitive muscle VSSCs. Comparison of the structures and activity of PIIIA to muscle-selective μ-conotoxins provides an insight into the structural requirements for inhibition of different TTX-sensitive sodium channels by μ-conotoxins.