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1、BiophysicalChemistry151(2010)54–60ContentslistsavailableatScienceDirectBiophysicalChemistryjournalhomepage:http://www.elsevier.com/locate/biophyschemTheeffectofcalciumbindingontheunfoldingbarrier:Akineticstudyonhomologousα-amylasesa,b,1a,1b,⁎,JörgFittera,⁎ArpanaK
2、umari,TobiasRosenkranz,ArvindM.KayasthaaResearchCentreJülich,ISB-2:MolecularBiophysics,D-52425Jülich,GermanybSchoolofBiotechnology,FacultyofScience,BanarasHinduUniversity,Varanasi-221005,IndiaarticleinfoabstractArticlehistory:Extremethermostabilitiesofproteinscan
3、beachievedbybindingco-factorstotheproteinstructures.ForReceived31March2010variousα-amylasesproteinstabilizationuponcalciumbindingisawell-knownphenomenon.InthepresentReceivedinrevisedform11May2010studythemechanismofstabilizationofthreehomologousα-amylaseswasinvest
4、igatedbymeasuringtheAccepted12May2010unfoldingkineticswithCDspectroscopy.ForthispurposethermalunfoldingkineticsofcalciumsaturatedAvailableonline19May2010andcalciumdepletedenzymeswereanalyzedbymeansofEyring-plots.Thefreeenergychangebetweenthenativeandthetransition
5、statewhichcharacterizedtheunfoldingbarrierheightwasfoundtobeproportionalKeywords:Alpha-amylasetothenumberofcalciumionsboundtotheproteinstructures.Forthemostthermostableα-amylasesProteinstabilitycalciumbindingcausedasignificantincreaseintheenthalpychange,whichwaspa
6、rtlycompensatedbyMulti-domainproteinincreasedentropychanges.Calciumbinding©2010ElsevierB.V.Allrightsreserved.ThermalunfoldingEyring-plot1.Introductionbecomeanimportantmodelsystemfortheinvestigationofthermaladaptationofmediumsizedenzymes[6–9].Inprincipleorganismsc
7、anliveunderharshconditionsandinInordertoelucidatethemechanismsofproteinstabilizationforα-extremeenvironments.Forexampleorganismsareadaptedtohighamylasesinmoredetail,atleasttwoaspectsareofparticulartemperatures,knownasthermophiles(growthtemperature50–importance.Fi
8、rst,inmostcasestheunfoldingtransitionsareirrevers-70°C)orhyperthermophiles(growthtemperaturesN80°C).Proteinsible,whichisrathercommonformulti-domainproteins[10,
