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1、BAmericanSocietyforMassSpectrometry,2012J.Am.Soc.MassSpectrom.(2012)23:1757Y1767DOI:10.1007/s13361-012-0430-yRESEARCHARTICLEEvidenceforthePreservationofNativeInter-andIntra-MolecularHydrogenBondsintheDesolvatedFK-BindingProtein·FK506ComplexProducedbyElectrosp
2、rayIonization1,3112JonathanT.S.Hopper,AndrewRawlings,JoséP.Afonso,DeborahChanning,21RobertLayfield,NeilJ.Oldham1SchoolofChemistry,UniversityofNottingham,UniversityPark,Nottingham,NG72RD,UK2SchoolofBiomedicalSciences,UniversityofNottingham,TheQueen’sMedicalCen
3、tre,Nottingham,NG72UH,UK3DepartmentofChemistry,PhysicalandTheoreticalChemistryLaboratory,UniversityofOxford,SouthParksRoad,Oxford,OX13QZ,UKAbstractItisnowwellestablishedthatelectrosprayionization(ESI)iscapableofintroducingnoncovalentproteinassembliesintoadeso
4、lvatedenvironment,therebyallowingtheiranalysisbymassspectrometry.Thedegreetowhichnativeinteractionsfromthesolutionphasearepreservedinthisenvironmentislessclear.Site-directedmutagenesisofFK506-bindingprotein(FKBP)hasbeenemployedtoprobespecificintra-andinter-mo
5、lecularinteractionswithinthecomplexbetweenFKBPanditsligandFK506.Collisionalactivationofwild-typeandmutant-FKBP•FK506ions,generatedbyESI,demonstratedthatremovalofnativeprotein–ligandinteractionsformedbetweenresiduesAsp37,Tyr82,andFK506significantlydestabilized
6、thecomplex.MutationofArg42toAla42,orTyr26toPhe26alsoresultedinlowerenergydissociationoftheFKBP·FK506complex.AlthoughtheseresiduesdonotformdirectH-bondstoFK506,theyinteractwithAsp37,ensuringitscorrectorientationtoassociatewiththeligand.Comparisonwithsolution-b
7、asedaffinitymeasurementsofthesemutantshasbeendiscussed,includingthestabilizationaffordedbyorderedwatermolecules.Ionmobilityspectrometry(IMS)hasbeenemployedtoprovidegas-phasestructuralinformationontheunfoldingofthecomplexes.The[M6++6H]complexesofthewild-typean
8、dmutantshavebeenshowntoresistunfoldingandretaincompactconformations.However,removalofthebasicArg42residuewasfoundtoinduce7+significantstructuralweakeningofthe[M+7H]complexwhenraisedtodiss
