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Article: Novel interactions identified between μ-conotoxin and the Na + channel domain I P-loop: Implications for toxin-pore binding geometry

TitleNovel interactions identified between μ-conotoxin and the Na + channel domain I P-loop: Implications for toxin-pore binding geometry
Authors
KeywordsChemicals And Cas Registry Numbers
Issue Date2003
PublisherCell Press. The Journal's web site is located at http://www.cell.com/biophysj/
Citation
Biophysical Journal, 2003, v. 85 n. 4, p. 2299-2310 How to Cite?
Abstractμ-Conotoxins (μ-CTX) are peptides that inhibit Na+ flux by blocking the Na+ channel pore. Toxin residue arginine 13 is critical for both high affinity binding and for complete block of the single channel current, prompting the simple conventional view that residue 13 (R13) leads toxin docking by entering the channel along the pore axis. To date, the strongest interactions identified are between μ-CTX and domain II (DII) or DIII pore residues of the rat skeletal muscle (Nav1.4) Na + channels, but little data is available for the role of the DI P-loop in μ-CTX binding due to the lack of critical determinants identified in this domain. Despite being an essential determinant of isoform-specific tetrodotoxin sensitivity, the DI-Y401C variant had little effect on μ-CTX block. Here we report that the charge-changing substitution Y401K dramatically reduced the μ-CTX affinity (∼300-fold). Using mutant cycle analysis, we demonstrate that K401 couples strongly to R13 (ΔΔG > 3.0 kcal/mol) but not R1, K11, or R14 (≪1 kcal/mol). Unlike K401, however, a significant coupling was detected between toxin residue 14 and DI-E403K (ΔΔG = 1.4 kcal/mol for the E403K-Q14D pair). This appears to underlie the ability of DI-E403K channels to discriminate between the GIIIA and GIIIB isoforms of μ-CTX (p < 0.05), whereas Y401K, DII-E758Q, and DIII-D1241K do not. We also identify five additional, novel toxin-channel interactions (>0.75 kcal/mol) in DII (E758-K16, D762-R13, D762-K16, E765-R13, E765-K16). Considered together, these new interactions suggest that the R13 side chain and the bulk of the bound toxin μ-CTX molecule may be significantly tilted with respect to pore axis.
Persistent Identifierhttp://hdl.handle.net/10722/91580
ISSN
2015 Impact Factor: 3.632
2015 SCImago Journal Rankings: 2.188
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorXue, Ten_HK
dc.contributor.authorEnnis, ILen_HK
dc.contributor.authorSato, Ken_HK
dc.contributor.authorFrench, RJen_HK
dc.contributor.authorLi, RAen_HK
dc.date.accessioned2010-09-17T10:21:41Z-
dc.date.available2010-09-17T10:21:41Z-
dc.date.issued2003en_HK
dc.identifier.citationBiophysical Journal, 2003, v. 85 n. 4, p. 2299-2310en_HK
dc.identifier.issn0006-3495en_HK
dc.identifier.urihttp://hdl.handle.net/10722/91580-
dc.description.abstractμ-Conotoxins (μ-CTX) are peptides that inhibit Na+ flux by blocking the Na+ channel pore. Toxin residue arginine 13 is critical for both high affinity binding and for complete block of the single channel current, prompting the simple conventional view that residue 13 (R13) leads toxin docking by entering the channel along the pore axis. To date, the strongest interactions identified are between μ-CTX and domain II (DII) or DIII pore residues of the rat skeletal muscle (Nav1.4) Na + channels, but little data is available for the role of the DI P-loop in μ-CTX binding due to the lack of critical determinants identified in this domain. Despite being an essential determinant of isoform-specific tetrodotoxin sensitivity, the DI-Y401C variant had little effect on μ-CTX block. Here we report that the charge-changing substitution Y401K dramatically reduced the μ-CTX affinity (∼300-fold). Using mutant cycle analysis, we demonstrate that K401 couples strongly to R13 (ΔΔG > 3.0 kcal/mol) but not R1, K11, or R14 (≪1 kcal/mol). Unlike K401, however, a significant coupling was detected between toxin residue 14 and DI-E403K (ΔΔG = 1.4 kcal/mol for the E403K-Q14D pair). This appears to underlie the ability of DI-E403K channels to discriminate between the GIIIA and GIIIB isoforms of μ-CTX (p < 0.05), whereas Y401K, DII-E758Q, and DIII-D1241K do not. We also identify five additional, novel toxin-channel interactions (>0.75 kcal/mol) in DII (E758-K16, D762-R13, D762-K16, E765-R13, E765-K16). Considered together, these new interactions suggest that the R13 side chain and the bulk of the bound toxin μ-CTX molecule may be significantly tilted with respect to pore axis.en_HK
dc.languageengen_HK
dc.publisherCell Press. The Journal's web site is located at http://www.cell.com/biophysj/ en_HK
dc.relation.ispartofBiophysical Journalen_HK
dc.subjectChemicals And Cas Registry Numbersen_HK
dc.subject.meshBinding Sitesen_HK
dc.subject.meshCell Lineen_HK
dc.subject.meshCells, Cultureden_HK
dc.subject.meshComputer Simulationen_HK
dc.subject.meshConotoxins - chemistry - pharmacologyen_HK
dc.subject.meshDose-Response Relationship, Drugen_HK
dc.subject.meshHumansen_HK
dc.subject.meshIon Channel Gating - drug effects - physiologyen_HK
dc.subject.meshKidney - drug effects - embryology - physiologyen_HK
dc.subject.meshMembrane Potentials - drug effects - physiologyen_HK
dc.subject.meshModels, Biologicalen_HK
dc.subject.meshMutagenesis, Site-Directeden_HK
dc.subject.meshPorosityen_HK
dc.subject.meshProtein Bindingen_HK
dc.subject.meshProtein Structure, Tertiaryen_HK
dc.subject.meshSodium Channels - chemistry - drug effects - physiologyen_HK
dc.subject.meshStructure-Activity Relationshipen_HK
dc.titleNovel interactions identified between μ-conotoxin and the Na + channel domain I P-loop: Implications for toxin-pore binding geometryen_HK
dc.typeArticleen_HK
dc.identifier.emailLi, RA:ronaldli@hkucc.hku.hken_HK
dc.identifier.authorityLi, RA=rp01352en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.pmid14507694-
dc.identifier.scopuseid_2-s2.0-0141530983en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0141530983&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume85en_HK
dc.identifier.issue4en_HK
dc.identifier.spage2299en_HK
dc.identifier.epage2310en_HK
dc.identifier.isiWOS:000185575400020-
dc.publisher.placeUnited Statesen_HK
dc.identifier.scopusauthoridXue, T=7005064190en_HK
dc.identifier.scopusauthoridEnnis, IL=6604033332en_HK
dc.identifier.scopusauthoridSato, K=7406409211en_HK
dc.identifier.scopusauthoridFrench, RJ=7202789440en_HK
dc.identifier.scopusauthoridLi, RA=7404724466en_HK

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