liguofu§33DStructureofProteins§3.1OverviewofProteinStructure§3.2ProteinSecondaryStructure§3.3TertiaryQuaternaryStructure§3.4ProteinDenaturationFolding
liguofu§3.3TertiaryQuaternaryStructureFibrousproteinsGlobularproteinsStructruralpatterns
liguofuGlobularproteinsMyoglobinHemoglobinMethodsfordeterminingthe3Dstructureofaprotein
liguofu
liguofuSpermwhalemyoglobin(肌红蛋白),theoxygencarrierinmuscle,wasthefirstproteintobeseeninatomicdetailbyX-rayanalysis(JohnKendrew,1950s,HeandMaxPerutzwontheNobelPrizeinChemistryin1962fordeterminingthecompleteatomicstructureofmyoglobinandhemeglobin).Theexistenceof?-heliceswereforthefirsttimedirectlyobservedinaprotein.?Themyoglobinmoleculecontainseight?-helices.?Allthe?-helicesareright-handed.?Allthepeptidebondsareintheplanartransconfiguration.?Thereisnoβ-pleatedsheetsobservedinthemolecule.Myoglobin
liguofuThemyoglobinmoleculehasadensehydrophobiccore.ManyhydrophobicRgroups(e.g.,Leu,Val,Met,Phe)arefoundtobeintheinteriorofthemyoglobinmolecule.Onlytwohydrophilichistidineresidueswerefoundintheinterioroftheprotein.AllbuttwoofthepolarRgroupsarelocatedontheoutersurfaceandhydrated.(Nonpolarresiduescanbealsopresentontheoutersurface!)Bendingaremadeofresiduesorsequencesthatarepatiblewith?-helicalstructure.AllProresiduesarefoundatbends.Myoglobin
liguofuTheflathemegroup(theprostheticgroup)wasrevealedtorestinacrevice(pocket).?Thehemegroupconsistsofacomplexorganicringstructure,protoporphyrin,whichisboundtoanironatominitsferrous(Fe2+)state.?Theironatomhassixcoordinationbonds,withfourintheplaneofandbondedtotheflatporphyrinmoleculeandtwoperpendiculartoit.?OneoftheperpendicularcoordinationbondsisboundtoanitrogenatomofaninteriorHisresidue.?Thesixthcoordinationservesas