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Article: Altered ionic selectivity of the sodium channel revealed by cysteine mutations within the pore

TitleAltered ionic selectivity of the sodium channel revealed by cysteine mutations within the pore
Authors
KeywordsChemicals And Cas Registry Numbers
Issue Date1997
PublisherRockefeller University Press. The Journal's web site is located at www.jgp.org/
Citation
Journal Of General Physiology, 1997, v. 109 n. 4, p. 463-475 How to Cite?
AbstractTo explore the role of pore-lining amino acids in Na+ channel ion- selectivity, pore residues were replaced serially with cysteine in cloned rat skeletal muscle Na+ channels. Ionic selectivity was determined by measuring permeability and ionic current ratios of whole-cell currents in Xenopus oocytes. The rSkM1 channels displayed an ionic selectivity sequence Na+>Li+>NH4 +>>K+>>Cs+ and were impermeable to divalent cations. Replacement of residues in domain IV showed significantly enhanced current and permeability ratios of NH4 + and K+, and negative shifts in the reversal potentials recorded in the presence of external Na+ solutions when compared to cysteine mutants in domains I, II, and III (except K1237C). Mutants in domain IV showed altered selectivity sequences: W1531C (NH4 +>K+>Na+≤Li+≃Cs+), D1532C, and G1533C (Na+>Li+≤NH4 +>K+>Cs+). Conservative replacement of the aromatic residue in domain IV (W1531) with phenylalanine or tyrosine retained Na+ selectivity of the channel while the alanine mutant (W1531A) reduced ion selectivity. A single mutation within the third pore forming region (K1237C) dramatically altered the selectivity sequence of the rSkM1 channel (NH4 +>+K+>Na+≤Li+≃Cs+) and was permeable to divalent cations having the selectivity sequence Ca2+≤Sr2+>Mg2+>Ba2+. Sulfhydryl modification of K1237C, W1531C or D1532C with methanethiosulfonate derivatives that introduce a positively charged ammonium group, large trimethylammonium moiety, or a negatively charged sulfonate group within the pore was ineffective in restoring Na+ selectivity to these channels. Selectivity of D1532C mutants could be largely restored by increasing extracellular pH suggesting altering the ionized state at this position influences selectivity. These data suggest that K1237 in domain III and W1531, D1532, and G1533 in domain IV play a critical role in determining the ionic selectivity of the Na+ channel.
Persistent Identifierhttp://hdl.handle.net/10722/91535
ISSN
2015 Impact Factor: 4.511
2015 SCImago Journal Rankings: 3.061
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorTsushima, RGen_HK
dc.contributor.authorLi, RAen_HK
dc.contributor.authorBackx, PHen_HK
dc.date.accessioned2010-09-17T10:20:58Z-
dc.date.available2010-09-17T10:20:58Z-
dc.date.issued1997en_HK
dc.identifier.citationJournal Of General Physiology, 1997, v. 109 n. 4, p. 463-475en_HK
dc.identifier.issn0022-1295en_HK
dc.identifier.urihttp://hdl.handle.net/10722/91535-
dc.description.abstractTo explore the role of pore-lining amino acids in Na+ channel ion- selectivity, pore residues were replaced serially with cysteine in cloned rat skeletal muscle Na+ channels. Ionic selectivity was determined by measuring permeability and ionic current ratios of whole-cell currents in Xenopus oocytes. The rSkM1 channels displayed an ionic selectivity sequence Na+>Li+>NH4 +>>K+>>Cs+ and were impermeable to divalent cations. Replacement of residues in domain IV showed significantly enhanced current and permeability ratios of NH4 + and K+, and negative shifts in the reversal potentials recorded in the presence of external Na+ solutions when compared to cysteine mutants in domains I, II, and III (except K1237C). Mutants in domain IV showed altered selectivity sequences: W1531C (NH4 +>K+>Na+≤Li+≃Cs+), D1532C, and G1533C (Na+>Li+≤NH4 +>K+>Cs+). Conservative replacement of the aromatic residue in domain IV (W1531) with phenylalanine or tyrosine retained Na+ selectivity of the channel while the alanine mutant (W1531A) reduced ion selectivity. A single mutation within the third pore forming region (K1237C) dramatically altered the selectivity sequence of the rSkM1 channel (NH4 +>+K+>Na+≤Li+≃Cs+) and was permeable to divalent cations having the selectivity sequence Ca2+≤Sr2+>Mg2+>Ba2+. Sulfhydryl modification of K1237C, W1531C or D1532C with methanethiosulfonate derivatives that introduce a positively charged ammonium group, large trimethylammonium moiety, or a negatively charged sulfonate group within the pore was ineffective in restoring Na+ selectivity to these channels. Selectivity of D1532C mutants could be largely restored by increasing extracellular pH suggesting altering the ionized state at this position influences selectivity. These data suggest that K1237 in domain III and W1531, D1532, and G1533 in domain IV play a critical role in determining the ionic selectivity of the Na+ channel.en_HK
dc.languageengen_HK
dc.publisherRockefeller University Press. The Journal's web site is located at www.jgp.org/en_HK
dc.relation.ispartofJournal of General Physiologyen_HK
dc.subjectChemicals And Cas Registry Numbersen_HK
dc.subject.meshAnimalsen_HK
dc.subject.meshCations, Divalent - metabolismen_HK
dc.subject.meshCell Membrane Permeability - physiologyen_HK
dc.subject.meshCysteine - genetics - metabolismen_HK
dc.subject.meshElectric Stimulationen_HK
dc.subject.meshElectrophysiologyen_HK
dc.subject.meshFemaleen_HK
dc.subject.meshHydrogen-Ion Concentrationen_HK
dc.subject.meshMembrane Potentials - physiologyen_HK
dc.subject.meshMuscle, Skeletal - metabolismen_HK
dc.subject.meshMutagenesis, Site-Directed - physiologyen_HK
dc.subject.meshMutation - physiologyen_HK
dc.subject.meshOocytes - metabolismen_HK
dc.subject.meshPatch-Clamp Techniquesen_HK
dc.subject.meshRatsen_HK
dc.subject.meshSodium Channels - genetics - metabolismen_HK
dc.subject.meshSulfhydryl Compounds - metabolismen_HK
dc.subject.meshXenopus laevisen_HK
dc.titleAltered ionic selectivity of the sodium channel revealed by cysteine mutations within the poreen_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.doi10.1085/jgp.109.4.463en_HK
dc.identifier.pmid9101405-
dc.identifier.scopuseid_2-s2.0-0030894992en_HK
dc.identifier.hkuros222525-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0030894992&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume109en_HK
dc.identifier.issue4en_HK
dc.identifier.spage463en_HK
dc.identifier.epage475en_HK
dc.identifier.isiWOS:A1997WT51900006-
dc.publisher.placeUnited Statesen_HK
dc.identifier.scopusauthoridTsushima, RG=7006183117en_HK
dc.identifier.scopusauthoridLi, RA=7404724466en_HK
dc.identifier.scopusauthoridBackx, PH=7006796226en_HK

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