Maurocalcine,acomponentofthevenomofScorpiomauruspalmatus,wasdiscoveredbyMichelDeWaard,co-founderofSmartox. Maurocalcine foldsaccordingtoaninhibitorcysteineknot.Suchas ImperatoxinA,Maurocalcine actsasahighaffinityagoNISTofthe type-1ryanodinereceptorexpressedinskeletalmuscleswithanaffinityinthe10nMrange. Maurocalcine inducesanincreaseinchannelopeningprobABIlityaccompaniedbysuddentransitionstolonglastingsubconductancestates. Maurocalcine hasalsobeencharacterizedasacellpenetratingpeptideanditspharmacologicalactivitycanbeobserveduponextracellularperfusion. Description:Productcode:07MAU001.Categories:Calciumchannels,Ryanodinereceptors.Tags:hadrucalcin,imperatoxin,ryanodine,RyR.AAsequence: Gly-Asp-Cys3-Leu-Pro-His-Leu-Lys-Leu-Cys10-Lys-Glu-Asn-Lys-Asp-Cys16-Cys17-Ser-Lys-Lys-Cys21-Lys-Arg-Arg-Gly-Thr-Asn-Ile-Glu-Lys-Arg-Cys32-Arg-OHDisulfidebonds: Cys3-Cys17,Cys10-Cys21 andCys16-Cys32Length(aa): 33Formula: C156H260N56O46S6MolecularWeight: 3858.8DaAppearance: WhitelyophilizedsolidSolubility: waterandsalinebufferCASnumber: notavailableSource: SyntheticPurityrate: >98%Reference:Redox-sensitivestimulationoftype-1ryanodinereceptorsbythescorpiontoxinmaurocalcine.CellCalciumThescorpiontoxinmaurocalcineactsasahighaffinityagonistofthetype-1ryanodinereceptorexpressedinskeletalmuscle.Here,weinvestigatedtheeffectsofthereducingagentdithiothreitolortheoxidizingreagentthimerosalontype-1ryanodinereceptorstimulationbymaurocalcine.MaurocalcineadditiontosarcoplasmicreticulumvesiclesactivelyloadedwithcalciumelicitedCa²⁺releasefromnativevesiclesandfromvesiclespre-incubatedwithdithiothreitol;thimerosaladditiontonativevesiclesafterCa²⁺uptakecompletionpreventedthisresponse.Maurocalcineenhancedequilibrium[³H]-ryanodinebindingtonativeandtodithiothreitol-treatedreticulumvesicles,andincreased5-foldtheapparentKiforMg²⁺inhibitionof[³H]-ryanodinebindingtonativevesicles.Singlecalciumreleasechannelsincorporatedinplanarlipidbilayersdisplayedalong-livedopensub-conductancestateaftermaurocalcineaddition.Thefractionaltimespentinthissub-conductancestatedecreasedwhenloweringcytoplasmic[Ca²⁺]from10μMto0.1μMoratcytoplasmic[Mg²⁺]≥30μM.At0.1μM[Ca²⁺],onlychannelsthatdisplayedpooractivationbyCa²⁺werereADIlyactivatedby5nMmaurocalcine;subsequentincubationwiththimerosalabolishedthesub-conductancestateinducedbymaurocalcine.Weinterprettheseresultsasanindicationthatmaurocalcineactsasamoreeffectivetype-1ryanodinereceptorchannelagonistunderreducingconditions.RonjatM, etal.(2013)Redox-sensitivestimulationoftype-1ryanodinereceptorsbythescorpiontoxinmaurocalcine. CellCalcium. PMID:23623374MaurocalcineinteractswiththecardiacryanodinereceptorwithoutinducingchannelmodificationWehavepreviouslyshownthatMCa(maurocalcine),atoxinfromthevenomofthescorpionMauruspalmatus,bindstoRyR1(type1ryanodinereceptor)andinducesstrongmodificationsofitsgatingbehaviour.Inthepresentstudy,weinvestigatedtheabilityofMCatobindtoandmodifythegatingprocessofcardiacRyR2.Byperformingpull-downexperimentsweshowthatMCainteractsdirectlywithRyR2withanapparentaffinityof150nM.ByexpressingdifferentdomainsofRyR2invitro,weshowthatMCabindstotwodomainsofRyR2,whicharehomologouswiththosepreviouslyidentifiedonRyR1.TheeffectofMCabindingtoRyR2wasthenevaluatedbythreedifferentapproaches:(i)[(3)H]ryanodinebindingexperiments,showingaveryweakeffectofMCa(upto1muM),(ii)Ca(2+)releasemeasurementsfromcardiacsarcoplasmicreticulumvesicles,showingthatMCaupto1muMisunabletoinduceCa(2+)release,and(iii)single-channelrecordings,showingthatMCahasnoeffectontheopenprobabilityorontheRyR2channelconductancelevel.Long-lastingopeningeventsofRyR2wereobservedinthepresenceofMCaonlywhentheioniccurrentdirectionwasoppositetothephysiologicaldirection,i.e.fromthecytoplasmicfaceofRyR2toitsluminalface.Therefore,despitetheconservedMCabindingabilityofRyR1andRyR2,functionalstudiesshowthat,incontrastwithwhatisobservedwithRyR1,MCadoesnotaffectthegatingpropertiesofRyR2.TheseresultshighlightadifferentroleoftheMCa-bindingdomainsinthegatingprocessofRyR1andRyR2.AltafajX, etal. (2007) Maurocalcineinteractswiththecardiacryanodinereceptorwithoutinducingchannelmodification.BiochemJ. PMID:17537000Chemicalsynthesisandcharacterizationofmaurocalcine,ascorpiontoxinthatactivatesCa(2+)releasechannel/ryanodinereceptorsMaurocalcineisanoveltoxinisolatedfromthevenomofthechactidscorpionScorpiomauruspalmatus.Itisa33-merbasicpeptidecross-linkedbythreedisulfidebridges,whichshares82%sequenceidentitywithimperatoxinA,ascorpiontoxinfromthevenomofPandinusimperator.Maurocalcineispeculiarintermsofstructuralpropertiessinceitdoesnotpossessanyconsensusmotifreportedsofarinotherscorpiontoxins.Duetoitslowconcentrationinvenom(0.5%oftheproteins),maurocalcinewaschemicallysynthesizedbymeansofanoptimizedsolid-phasemethod,andpurifiedafterfolding/oxidationbyusingbothC18reversed-phaseandionexchangehigh-pressureliquidchromatographies.Thesyntheticproduct(sMCa)wascharacterized.Thehalf-cystinepairingpatternofsMCawasidentifiedbyenzyme-basedcleavageandEdmansequencing.ThepairingswereCys3-Cys17,Cys10-Cys21,andCys16-Cys32.Invivo,thesMCawaslethaltomicefollowingintracerebroventricularinoculation(LD(50),20microg/mouse).Invitro,electrophysiologicalexperimentsbasedonrecordingsofsinglechannelsincorporatedintoplanarlipidbilayersshowedthatsMCapotentlyandreversIBLymodifieschannelgatingbehaviorofthetype1ryanodinereceptorbyinducingprominentsubconductancebehavior.Fajloun,Z., etal.(2000)Chemicalsynthesisandcharacterizationofmaurocalcine,ascorpiontoxinthatactivatesCa(2+)releasechannel/ryanodinereceptors, FEBSLett. PMID:10713267Anewfoldinthescorpiontoxinfamily,associatedwithanactivityonaryanodine-sensitivecalciumchannelWedeterminedthestructureinsolutionby(1)Htwo-dimensionalNMRofMaurocalcinefromthevenomofScorpiomaurus.Thistoxinhasbeendemonstratedtobeapotenteffectorofryanodyne-sensitivecalciumchannelfromskeletalmuscles.ThisisthefirstdescriptionofascorpiontoxinwhichfoldsfollowingtheInhibitorCystineKnotfold(ICK)alreadydescribedfornumeroustoxicandinhibitorypeptides,aswellasforvariousproteaseinhibitors.Itsthreedimensionalstructureconsistsofacompactdisulfide-bondedcorefromwhichemergeloopsandtheN-terminus.Adouble-strandedantiparallelbeta-sheetcomprisesresidues20-23and30-33.Athirdextendedstrand(residues9-11)isperpendiculartothebeta-sheet.MaurocalcinestructuremimicstheactivatingsegmentofthedihydropyridinereceptorII-IIIloopandisthereforepotentiallyusefulfordihydropyridinereceptor/ryanodinereceptorinteractionstudies.Mosbah,A., etal.(2000)Anewfoldinthescorpiontoxinfamily,associatedwithanactivityonaryanodine-sensitivecalciumchannel, Proteins. PMID:10861934