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

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

=-45oto-50o.4Thebsheets5Extremelycolorfulproteinstructures6immunoglobulindomain免疫球蛋白結(jié)構(gòu)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)鹽酸胍131929年在波士頓召開(kāi)的第13屆國(guó)際生理學(xué)會(huì)上他提出蛋白質(zhì)變性學(xué)說(shuō)：認(rèn)為天然蛋白質(zhì)分子不是一長(zhǎng)的直鏈而是一緊密的結(jié)構(gòu)；這種結(jié)構(gòu)是借肽鍵之外的其他鍵，將肽鏈的不同部分連接而形成的，所以容易被物理及化學(xué)的力所破壞，即從有規(guī)則的折疊排列形式變成不規(guī)則及松散的形式。這個(gè)學(xué)說(shuō)對(duì)于研究蛋白質(zhì)大分子的高級(jí)結(jié)構(gòu)有重要價(jià)值。

吳憲(1893～1959)14Proteinsequencedeterminesitstertiarystructure.TheNobelPrizeinChemistry1972"forhisworkonribonuclease,especiallyconcerningtheconnectionbetweentheaminoacidsequenceandthebiologicallyactiveconformation”.ChristianB.AnfinsenThisistrueforonlyasmallnumberofproteins.15Proteinshavehighlyvariousstructurestoperformhighlyvariousfunctions.16ProteinfunctionsStructuralproteins結(jié)構(gòu)性蛋白Activelyfunctionalproteins功能性蛋白keratin,collagen,cytoskeleton,cell-celladhesion,etcenzyme,signaltransduction,transportation,immunity,regulatingproteins………17“permanentwaving”silkfibroin絲心蛋白-keratin角蛋白18collagen膠原蛋白Gly-X-Yrepeat(XisoftenPro;YisoftenHyp)19cytoskeleton細(xì)胞骨架actin微絲microtubule微管OpossumKidneyEpithelialCells(OKLine)/gallery/cells/ok/okexlarge3.html2021myoglobin肌紅蛋白153aminoacidresidues,>70%in

–helix;bindingahemegroup.22Hemegroup血紅素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血紅蛋白/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