Proteinstructure王春光2017-09-26chunguangwang@tongji.edu.cn2Peptidebond肽键3Numberofnegativelychargedresidues(Asp+Glu):9Numberofpositivelychargedresidues(Arg+Lys):17Lysozyme溶菌酶Primarysequenceof129residues:KVFGRCELAAAMKRHGLDNYRGYSLGNWVCAAKFESNFNTQATNRNTDGSTDYGILQINSRWWCNDGRTPGSRNLCNIPCSALLSSDITASVNCAKKIVSDGNGMNAWVAWRNRCKGTDVQAWIRGCRLTheoreticalpI:9.32(http://web.expasy.org/cgi-bin/protparam/protparam)4a-helix(a-螺旋)b-sheet(b-折叠)Lysozymestructure(PDB3LYM)5Ana-helixinlysozyme:RCELAAAMKRH(colorcode:CNOS)6Theahelix•Tomakeoptimaluseofinternalhydrogenbonds.•Everyhelicalturnextendsabout5.4Åalongtheaxis.•Onlyright-handedhelix.•Everyhelicalturnincludes3.6residues,sothateveryresidueturns100degrees.5.4Å7Interactionbetweensidechainsofresidueiandi+3ori+4;Prorarelyappearsina-helix.Ana-helixinlysozyme:RCELAAAMKRH90°8LinusPauling(1901-1994)gottheNobelPrizeinChemistryin1954“forhisresearchintothenatureofthechemicalbondanditsapplicationtotheelucidationofthestructureofcomplexsubstances”.9Coiled-coilstructure(MyosinIIcoiled-coil,PDB2FXO)90°Heptadrepeats(七元重复)insequence:-(abcdefg)n-a,d:hydrophobic;e,g:oppositelycharged.10abcdefgAnexample:coiled-coilfrommyosinII(PDB2FXO)-MASMKEEFTRLKEALEKSEAR-(MyosinIIcoiled-coil,PDB2FXO)-MASMKEEFTRLKEALEKSEAR-11123and4-strandedcoiled-coilarealsopossible.FigureadaptedfromProteins:Structure,FunctionandGenetics7:1-15,(1990).13Lysozymestructure(PDB3LYM)a-helix(a-螺旋)b-sheet(b-折叠)14Theb-sheet15Theb-sheet16Thebsheets（反平行的）（平行的）1718Extremelycolorfulproteinstructures19Immunoglobulin免疫球蛋白PDB:1IGTdomain结构域subunit亚基20Proteinquaternarystructures（四级结构）2122Denaturation（变性）ofproteinsAlossofthree-dimensionalstructuresufficienttocauselossoffunction.(http://matcmadison.edu/biotech/resources/proteins/labManual/images/220_04_021.gif)23MostproteinscanbedenaturedbyheatingMedicalsterilization.Anexceptionisthethermophilicbacteria.24Chaotropicreagentsdisturbthehydrogenbondnetworkinproteins.O║NH2─C─NH2NH2+║Cl-NH2─C─NH2...
