生物化学教学课件：protein-2

Proteins2014-09-232a-helixb-sheetLysozyme溶菌酶Primarysequenceof129residues:KVFGRCELAAAMKRHGLDNYRGYSLGNWVCAAKFESNFNTQATNRNTDGSTDYGILQINSRWWCNDGRTPGSRNLCNIPCSALLSSDITASVNCAKKIVSDGNGMNAWVAWRNRCKGTDVQAWIRGCRLStructure(PDB3LYM):TheahelixTomakeoptimaluseofinternalhydrogenbonds.O---------------H

║│─C─(NH─CH─CO)3─N─Everyhelicalturnextendsabout5.4Åalongtheaxis.Onlyright-handedhelix.Everyhelicalturnincludes3.6residues,sothateveryresidueturns100degrees.f=-60º;

=-45ºto-50º.4Thebsheets5Extremelycolorfulproteinstructures6immunoglobulindomain免疫球蛋白结构域PDB:1IGT7Proteinquaternarystructuresareoftensymmetricallyorganized.8910DenaturationofproteinsAlossofthree-dimensionalstructuresufficienttocauselossoffunction.(/biotech/resources/proteins/labManual/images/220_04_021.gif)11MostproteinscanbedenaturedbyheatMedicalsterilization.Anexceptionisthethermophilicbacteria.12Chaotropicreagentsdisturbthehydrogenbondnetworkinproteins.O

║NH2─C─NH2NH2+

║Cl-

NH2─C─NH2Urea尿素Guanidinehydrochloride(GdnHCl)盐酸胍131929年在波士顿召开的第13届国际生理学会上他提出蛋白质变性学说：认为天然蛋白质分子不是一长的直链而是一紧密的结构；这种结构是借肽键之外的其他键，将肽链的不同部分连接而形成的，所以容易被物理及化学的力所破坏，即从有规则的折叠排列形式变成不规则及松散的形式。这个学说对于研究蛋白质大分子的高级结构有重要价值。

吴宪(1893～1959)14Proteinsequencedeterminesitstertiarystructure.TheNobelPrizeinChemistry1972"forhisworkonribonuclease,especiallyconcerningtheconnectionbetweentheaminoacidsequenceandthebiologicallyactiveconformation”.ChristianB.AnfinsenThisistrueforonlyasmallnumberofproteins.15Proteinshavehighlyvariousstructurestoperformhighlyvariousfunctions.16ProteinfunctionsStructuralproteins结构性蛋白Activelyfunctionalproteins功能性蛋白keratin,collagen,cytoskeleton,cell-celladhesion,etcenzyme,signaltransduction,transportation,immunity,regulatingproteins………17“permanentwaving”silkfibroin丝心蛋白-keratin角蛋白18collagen胶原蛋白Gly-X-Yrepeat(XisoftenPro;YisoftenHyp)19cytoskeleton细胞骨架actin微丝microtubule微管OpossumKidneyEpithelialCells(OKLine)/gallery/cells/ok/okexlarge3.html2021myoglobin肌红蛋白153aminoacidresidues,>70%in

–helix;bindingahemegroup.22Hemegroup血红素23Protein-ligandinteractionP+LPLKa=[PL][P][L]Kd=[P][L][PL]Y=BindingsiteoccupiedTotalbindingsite[PL][PL]+[P]==[L][L]+Kd24myoglobin+O2

myoglobin·O2Y=[L][L]+Kd=[O2][O2]+[O2]0.5=pO2pO2+P5025Hemoglobin血红蛋白/wiki/HemoglobinTwosubunitsof141residuesandtwo

subunitsof146residues.26myogloblin27Hemogloblinαchain28myogloblin&hemoglobin29Myoglobin:O2storageHemoglobin:O2transportation30Y=[pO2]n[pO2]n+P50nn=1,hyperboliccurve;Singleorindependentbinding;n>1,sigmoidalcurve;cooperativebinding.Hb+nO2Hb·(O2)nHillcoefficient,n,reflectsthedegreeofcooperativity.31/wiki/HemoglobinHemoglobinisanallostericprotein.32SomethingelsetoknowabouthemoglobinHemoglobinbindsCOwithhigheraffinity;Sickle-cellanem