生物大分子结构与功能相互作用力第节第节1,thesecondarystructures2,Supersecondarystructuresanddomains3,Toolstoinvestigatetheproteinconformation4,globularproteinsandSCOP5,fibrousproteinsProteinSecondaryStructure■Secondarystructureistheregulararrangementofaminoacidresiduesinasegmentofapolypeptidechain,inwhicheachresidueisspatiallyrelatedtoitsneighborsinthesameway、■Themostmonsecondarystructuresaretheαhelix,theβconformation,andβturns、■Thesecondarystructureofapolypeptidesegmentcanbepletelydefinediftheφandψanglesareknownforallaminoacidresiduesinthatsegment、10papersfromLinusPaulingandcolleaguespublishedinPNAS,1951αhelix310helixπhelix:theoreticallypossible,butneverfoundintheproteinsßsheet:parallelandanti-parallelαhelixParametersoffiveactualortheoreticalsecondarystructures:αhelix:thebackboneofthepolypeptidechainisextendedintohelicalstructureWhichIsbuiltupfromonecontinuousregion、大家有疑问的，可以询问和交流3、6residuesperturnwithhydrogenbondsbetweenC’=OofresiduesnandNHofresiduesn+4、Theendofαhelicesarepolarandarealmostatthesurfaceofproteinmolecules310helixIdealizedhelices:HydrogenbondingpatternsforfourhelicesTheαhelixhasadipolemomentSomeaminoacidsarepreferredinαhelix:Ala(A),Glu(E),Leu(L),andMet(M)aregoodαhelicesformers、2)Pro(P),Gly(G),Tyr(Y)andSer(S)areveryPoorformers3)Themostmonlocationforanαhelixinaproteinstructureisalongtheoutsideoftheprotein,withonesidefacingthesolutionandtheothersidefacingthehydrophobicinterioroftheprotein、4)αhelicesthatacrossmembranareinaHydrophobicenvironment,mostoftheirsideChainsarehydrophobicSaccharomycescerevisiaemitochondrialthioredoxin3MembraneProtein1)βsheet:thebackboneofthepolypeptidechainisextendedintoazigzagstructure、2)βsheetisbuiltupfromabinationofseveralregionsofthepolypeptidechain、3)Thelengthrangfrom5to10residues、Theaminoacidecanallruninthesamebiochemicaldirection,amioterminaltocarboxyterminalTwoformshaveadistinctivepatternofhydrogen-bondingβsheetcanalsobineintomixedβsheet(About20%ofknownproteinstructuresaremixed)Almostalltheβsheethavetwi