μ-ConotoxinPIIIA (mu-conotoxinPIIIA)isaconotoxinthathasbeenisolatedfromthevenomoftheconeConuspurpurascens. μ-conotoxinPIIIA demonstratesahigheraffinityforthemammalianmusclesodiumchannel Nav1.4 (IC50 ~44nM)thanfortheCNSNav1.2subtype(IC50 ~640 nm). μ-ConotoxinPIIIA blocks more irreversIBLyamphibian muscle sodium channels thanmammalianones.
Description:
AAsequence: H-pGlu-Arg-Leu-Cys4-Cys5-Gly-Phe-Hyp-Lys-Ser-Cys11-Arg-Ser-Arg-Gln-Cys16-Lys-Hyp-His-Arg-Cys21-Cys22-NH2
(DisulfidebondsbetweenCys4-Cys16,Cys5-Cys21 andCys11-Cys22)
Length(aa): 22
Formula: C103H165N40O28S6
MolecularWeight: 2604.10Da
Appearance:Whitelyophilizedsolid
Solubility: waterandsalinebuffer
CASnumber:
Source: Synthetic
Purityrate: >97%
Reference:
Mechanismofμ-ConotoxinPIIIABindingtotheVoltage-GatedNa+ChannelNaV1.4
Severalsubtypesofvoltage-gatedNa+(NaV)channelsareimportanttargetsforpainmanagement.μ-ConotoxinsisolatedfromvenomsofconesnailsarepotentandspecificblockersofdifferentNaVchannelisoforms.Theinhibitoryeffectofμ-conotoxinsonNaVchannelshasbeenexaminedextensively,butthemechanismoftoxinspecificityhasnotbeenunderstoodindetail.Heretheknownstructureofμ-conotoxinPIIIAandamodeloftheskeletalmusclechannelNaV1.4areusedtoelucidateelementsthatcontributetothestructuralbasisofμ-conotoxinbindingandspecificity.ThemodelofNaV1.4isconstructedbasedonthecrystalstructureofthebacterialNaVchannel,NaVAb.Sixdifferentbindingmodes,inwhichthesidechainofeachofthebasicresiduescarriedbythetoxinprotrudesintotheselectivityfilterofNaV1.4,areexaminedinatomicdetailusingmoleculardynamicssimulationswithexplicitsolvent.Thedissociationconstants(Kd)computedfortwoselectedbindingmodesinwhichLys9orArg14fromthetoxinprotrudesintothefilterofthechannelarewithin2fold;bothvaluesincloseproximitytothosedeterminedfromdoseresponsedatafortheblockofNaVcurrents.ToexplorethemechanismofPIIIAspecificity,adoublemutantofNaV1.4mimickingNaVchannelsresistanttoμ-conotoxinsandtetrodotoxinisconstructedandthebindingofPIIIAtothismutantchannelexamined.ThedoublemutationcausestheaffinityofPIIIAtoreducebytwoordersofmagnitude.
ChenR., etal.(2014) Mechanismofμ-ConotoxinPIIIABindingtotheVoltage-GatedNa+ChannelNaV1.4. PLoSOne. PMID24676211
Solutionstructureofmu-conotoxinPIIIA,apreferentialinhibitorofpersistenttetrodotoxin-sensitivesodiumchannels
Mu-conotoxinsarepeptideinhibitorsofvoltage-sensitivesodiumchannels(VSSCs).Syntheticformsofmu-conotoxinsPIIIAandPIIIA-(2-22)werefoundtoinhibittetrodotoxin(TTX)-sensitiveVSSCcurrentbuthadlittleeffectonTTX-resistantVSSCcurrentinsensoryganglionneurons.Inratbrainneurons,thesepeptidespreferentiallyinhibitedthepersistentoverthetransientVSSCcurrent.RADIoligandbindingassaysrevealedthatPIIIA,PIIIA-(2-22),andmu-conotoxinsGIIIBdiscriminatedamongTTX-sensitiveVSSCsinratbrain,thattheseandGIIICdiscriminatedamongthecorrespondingVSSCsinhumanbrain,andGIIIAhadlowaffinityforneuronalVSSCs.(1)HNMRstudiesfoundthatPIIIAadoptstwoconformationsinsolutionduetocis/transisomerizationathydroxyproline8.Themajortransconformationresultsinathree-dimensionalstructurethatissignificantlydifferentfromthepreviouslyidentifiedconformationofmu-conotoxinsGIIIAandGIIIBthatselectivelytargetTTX-sensitivemuscleVSSCs.ComparisonofthestructuresandactivityofPIIIAtomuscle-selectivemu-conotoxinsprovidesaninsightintothestructuralrequirementsforinhibitionofdifferentTTX-sensitivesodiumchannelsbymu-conotoxins.
Nielsen,K.J., etal. (2002)Solutionstructureofmu-conotoxinPIIIA,apreferentialinhibitorofpersistenttetrodotoxin-sensitivesodiumchannels, JBiolChem. PMID: 12006587
Distinctionamongneuronalsubtypesofvoltage-activatedsodiumchannelsbymu-conotoxinPIIIA
Thefunctionalpropertiesofmostsodiumchannelsaretoosimilartopermitidentificationofspecificsodiumchanneltypesunderlyingmacroscopiccurrent.Suchdiscriminationwouldbeparticularlyadvantageousinthenervoussysteminwhichdifferentsodiumchannelfamilyisoformsarecoexpressedinthesamecell.Totestwhethermembersofthemu-conotoxinfamilycandiscriminateamongknownneuronalsodiumchanneltypes,weexaminedsixtoxinsfortheirABIlitytoblockdifferenttypesofheterologouslyexpressedsodiumchannels.PIIIAmu-conotoxinblockedratbraintypeII/IIA(rBII/IIA)andskeletalmusclesodiumcurrentatconcentrationsthatresultedinonlyslightinhibitionofratperipheralnerve(rPN1)sodiumcurrent.RecordingsfromvariantlinesofPC12cells,whichselectivelyexpresseitherrBII/IIAorrPN1channelsubtypes,verifiedthatthedifferentialblockbyPIIIAalsoappliedtonativesodiumcurrent.ThesensitivitytoblockbyPIIIAtoxinwasthenusedtodiscriminatebetweenrBII/IIAandrPN1sodiumcurrentsinNGF-treatedPC12cellsinwhichbothmRNAsareinduced.Duringthefirst24hrofNGF-treatment,PN1sodiumchannelsaccountedforover90%ofthesodiumcurrent.However,overtheensuing48hrperiod,asharpriseintheproportionofrBII/IIAsodiumcurrentoccurred,confirmingtheidea,basedonpreviousmRNAmeasurements,thattwodistinctsodiumchanneltypesappearsequentiallyduringneuronaldifferentiationofPC12cells.
Safo,P., etal. (2000)Distinctionamongneuronalsubtypesofvoltage-activatedsodiumchannelsbymu-conotoxinPIIIA, JNeurosci. PMID: 10627583
mu-ConotoxinPIIIA,anewpeptidefordiscriminatingamongtetrodotoxin-sensitiveNachannelsubtypes
Wereportthecharacterizationofanewsodiumchannelblocker,mu-conotoxinPIIIA(mu-PIIIA).Thepeptidehasbeensynthesizedchemicallyanditsdisulfidebridgingpatterndetermined.Thestructureofthenewpeptideis:[sequence:seetext]whereZ=pyroglutamateandO=4-trans-hydroxyproline.WedemonstratethatArginine-14(Arg14)isakeyresidue;substitutionbyalaninesignificantlydecreasesaffinityandresultsinatoxinunabletoblockchannelconductancecompletely.Thus,likealltoxinsthatblockatSiteI,mu-PIIIAhasacriticalguanidiniumgroup.Thispeptideisofexceptionalinterestbecause,unlikethepreviouslycharacterizedmu-conotoxinGIIIA(mu-GIIIA),itirreversiblyblocksamphibianmuscleNachannels,providingausefultoolforsynapticelectrophysiology.FurThermore,thediscoveryofmu-PIIIApermitstheresolutionoftetrodotoxin-sensitivesodiumchannelsintothreecategories:(1)sensitivetomu-PIIIAandmu-conotoxinGIIIA,(2)sensitivetomu-PIIIAbutnottomu-GIIIA,and(3)resistanttomu-PIIIAandmu-GIIIA(examplesineachcategoryareskeletalmuscle,ratbrainTypeII,andmanymammalianCNSsubtypes,respectively).Thus,mu-conotoxinPIIIAprovidesakeyforfurtherdiscriminatingpharmacologicallyamongdifferentsodiumchannelsubtypes.
Shon,K.J., etal. (1998)mu-ConotoxinPIIIA,anewpeptidefordiscriminatingamongtetrodotoxin-sensitiveNachannelsubtypes, JNeurosci. PMID: 9614224
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