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By Alan Hart,2014-02-18 17:53
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Positive

    Positive

    change(DeltaV(u))fortheunfoldingare5.9kcal/moland

    160ml/mol,respectively.ItWasfoundthatNaC1andsucrose significantlystabilizetheproteinfromunfoldingandthestabilizationisassociatednotonlywi

    thanincreaseinDeltaG(u1

    butalsowithadecreaseinDeltaV(u).Thepressuredumpstudiesof23

    kDaproteinrevealanegativeactivationvolumefor

    unfolding(.66.2ml/mo1)andapositiveactivationvolumeforrefolding(84.1ml/mo1),indic

    atingthat,intermsofsystem

    volume,theproteintransitionstateliesbetweenthefoldedandunfoldedstates. Examinationofthetemperatureeffecton

    theunfoldingkineticsindicatesthatthethermalexpansibilityofthetransitionstateandtheunf

    oldedstateof23.kDaprotein

    areclosertoeachotherandtheyarelargerthanthatofthenativestate.Thediversepressure

    refoldingpathwaysof23-kDa

    proteininsomeconditionswererevealedinpressure-jumpkinetics. Keywords:rRANSFORMINFRARED

    SPECTROSCOPY;DERIVATIVEUV-SPECTROSCOPY;NUCLEAR-MAGNETIC. RESONANCE;HIGHHYDROSTATIC-PRESSURE;OXYGEN-EVOLVINGCOMPLEX;X.RAY-SCATTERIrNG;STAPHYLO-

    COCCALNUCLEASE;DENATUREDSTATE:FOLDGREACTIONS:TRANSnION.STATE

    BIOPHYSICALJOURNAL2005,88(2):1264-1275

    Positivechargesonlysineresiduesoftheextrinsic18kDaproteinare importanttoitselectrostaticinteractionwithspinachphotosystemII membranes

    GaoJP,YongZH,ZhangF,RuanKC,XuCH,ChenGY

    ChineseAcadSci,ShanghailnstBiolSci,lnstPlantPhysiol&Ecol,345LinglingLu,Shanghai,200032PeoplesRChina

    ChineseAcadSci,ShanghailnstBiolSci,lnstPlantPhysiol&Ecol,Shanghai,200032PeoplesRChina

    ChineseAcadSci,ShanghailnstBiolSci,LabProteom,lnstBiochem&CellBiol,Shanghai,20003IPeoplesRChina

    ZhejiangUniv,CoilSci,Hangzhou,310029PeoplesRChina

    ChineseAcadSci,GradSch,Shanghai,200032PeoplesRChina

    Abstract:TodeterminethecontributionofchargedaminoacidstobindingwiththephotosystemIIcomplex(PSII),the

    aminoorcarboxylgroupsoftheextrinsic18kDaproteinweremodified,?

    imN?succinimidylpropionate(NSP)orglycine

    methylester(GME)inthepresenceofawater

    solublecarbodiimide,respectively.Basedonisoelectricpointshift,410and

    10

    14aminogroupsweremodifiedinthepresenceof2and4mMNSP,respectively.Similarly,3-4carboxylgroupswere

    modifiedbyreaction'100mMGME.NeutralizationofnegativelychargedcarboxylgroupsGMEdidnotalterthe

    bindingactivityoftheextrinsic18kDaprotein.However,theNSP

    modified18kDaprotein,inwhichthepositivelycharged

    aminogroupshadbeenmodifiedtounchargedmethylesters,failedtobindwiththePSIImembraneinthepresenceofthe

    extrinsic23kDaprotein.111isdefectcannotbeattributedtostructuralorconformationalalterationsimposedbychemical

    modification,asthefluorescenceandcirculardichroismspectraamongnative,GME

    andNSPmodifiedextrinsic18kDa

    proteinsweresimilar.Thus.wehaveconcludedthatthepositivechargesoflysylresiduesintheextrinsic18kDaproteinare

importantforitsinteraction,?

    imPSIImembranesinthepresenceoftheextrinsic23kDaprotein.Furthermore,itwasfound thatthenegativechargesofcarboxylgroupsofthisproteindidnotparticipateinbindingwiththeextrinsic23kDaprotein

    associatedwithPSIImembranes.

    Keywords:extrinsic18kDaprotein;circulardichroism;electrostaticinteraction;chemicalmodification

    ACTABIOCHIMICAETBIOPHYSICASINICA2005,37(11):737742

    

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