Download In order to carry out their functions, proteins need to move. Scientists

In order to carry out their functions, proteins need to move. Scientistsatthe
IBSGrenobleandEPFL,incollaborationwithENSLyon,havedevelopeda
newapproachtothestudyproteinmotionswithunprecedentedaccuracy.
Byfreezingproteinsdowntoverylowtemperatures,researchersslowly
heatuptheproteinandwatchthedifferentcomponentsoftheproteinas
theycombinetoproducethedynamicsthatareessentialforfunction.
Proteinsarecomplexmachinesthatareinconstantmotion,movingcontinuously
inordertocarryouttheirfunctions.Theirmultiplecomponentatomsalsohave
theirindividualmotionpatterns,makingtheentireproteinasystemofnon‐stop
highlycomplexmovement.Understandinghowaproteinmovesisthekeyto
developingdrugsthatcanefficientlyinteractwithit.Butbecauseofits
complexity,proteinmotionhasbeennotoriouslydifficulttostudy.Scientistsat
IBS‐Grenoble,EPFLandENS‐Lyon,havedevelopedanewmethodforstudying
proteinmotionbyfirstfreezingproteinsandthenslowly“wakingthemup”with
increasingtemperature.ThebreakthroughmethodispublishedinScience.
Proteinmotionishighlycomplex
Motionispartofaprotein’sfunction,allowingittoadjustits3Dshapeand
interactwithothermoleculeslikebiologicalmoleculesandsyntheticdrugs.
These“functional”motionshoweverarecomplex,andcanbethoughtasthe
mechanismofawatch,wheremotionsbetweeninterlockingcogsandsprings,at
differenttimescales,resultinthesmoothmovementofthehands.
Inaproteinthecogsandspringsarethemoleculesthatmakeitup:aminoacids
formitsbackboneeachwithside‐chainsofdifferentmoleculesbranchingouton
allsidesinthreedimensions.Inaddition,watermoleculesboundtotheprotein
aswellasinthesolutionwhereitexists,e.g.thecell’scytoplasm,addevenmore
layersofmotionaldetailtothesystem.Proteinmotionseemsalmostchaoticin
itscomplexity,butsomehowcombinestoprovidethebiologicalfunction
essentialforlife.
Freeze,sleep,wakeup,andmove
TheteamofscientistsledbyMartinBlackledgeandLyndonEmsleyhave
developedaninnovativesolutiontothemotionproblem:freezetheproteinsand
thenwatchthem“wakeup”fromdeepsleep.Proteinmotiondependsonenergy,
andtemperatureallowstheresearcherstodialmoreenergyintothesystemina
controlledway.Byfreezingproteinsdowntotemperaturesbetween‐168°Cto
7°C,theywereabletoalmostcompletelystopallmotion,thenslowlyraisethe
temperaturetothepointwheretheproteincouldregaintheirnaturalmotions,
measuringthedynamicsoftheproteinalongtheway.Thisway,itwaspossible
tolookateachmotionaproteinexperiencesindividuallyand–moreimportantly
–intherightorder.
Inordertodetecttheindividualmotionsofproteins,thescientistsuseda
spectroscopictechniquecallednuclearmagneticresonance(NMR),which
exploitsthemagneticpropertiesofcertainatomslikehydrogen,nitrogenand
carbon.Becausetheproteinsinthisstudyneededtobefrozendown,the
researchteamhadtoadjusttheirNMRmethodologytoworkwithsamplesat
verylowtemperatures,allowingconsistentreadings,andkeepdoingsoasthe
temperatureincreasedto“waketheproteinsup”.Tomakelifemoredifficult,
samplesthatarefrozensolidaredifficulttoreadinNMR,sointhisstudythe
tubecontainingtheproteinshadtoalsobeconstantlyspinningataspecific
(“magic”)angletotheNMR’smagneticfield,inordertoimproveresolution.
Finally,everyNMRexperimenttookdaystoperform.Thesecomplicationswere
overcomebyusinganewlydevelopeddevicethathasbeenspecificallydesigned
toworkwithNMRatlowandchangingtemperatures,combinedwithaprecise
rotorsystemthatcouldspinthesampleoverlongperiodsoftime.
Ahierarchyofmotion
Usingtheirinnovativeapproach,theBlackledgeandEmsleyteamsfoundthatthe
sequenceofproteinmotionsfollowsaspecifichierarchyastemperature
increases:firsttheprotein’ssolutionmolecules,thentheprotein’sside‐chains
andwatermolecules,andfinallytheprotein’sbackbone.Thesequence
culminatesatafunctionallyactiveproteinattemperaturesevenaslowas‐53°C,
wellbelowphysiologicallevels.Thismeansthatthe“wakingup”methodisvery
effectiveforstudyingthemotionsofaproteinindividuallyandsequentially,
withoutdeviatingfromrealisticconditionsinacell.
ThisworkrepresentsacollaborationbetweenIBSGrenobleCEA/CNRS/UJF,EPFL’s
LaboratoryofMagneticResonanceandCNRS/ENS‐Lyon.
Reference
LewandowskiJ.R,HalseME,BlackledgeM,Emsley,L.Directobservationof
hierarchicalproteindynamics.ScienceXXXXXX.DOI:XXXXXXXXX