课件-生物化学chapter5.endomembrane system or intracellular细胞质基质或胞质溶胶

5.Cytoplasm细胞质：Cytoplasm(细胞质Cytoplasm:Allofgel-like(胶状的)andgranular(颗粒状substancesexceptfornucleus(细胞核)ornuclearzone(核区)enclosedbyplasmaComponents(成分ofCytosol细胞质基质或胞质溶胶dissolvednutrients(aminoacids,fattyacids,saccharides)andwasteproductsdissolvedmacromoleculessuchasRNAsandproteinsmanysalts无机离子andOrganelles(细胞器):Membrane-boundedorganellesandRibosomes（prokaryotes-原核生物）？Cytoplasmicinclusions(包涵物granuleswithshapesandwithoutmetabolic---glycogen糖原)granulesstoringfatdropstoringfattyacidsandsterols（固醇,甾酮secretorygranulesstoringproenzyme（酶原3胰腺外腺酶原颗粒42)FunctionsofMetabolicpathwaysbiochemicalreactionsandUbiquitin-proteasomesystem（泛素-蛋白酶体系统）MaintenanceofcellshapeandstabilizingtheintracellularParticipatingincellsignalFunctionsof 5Thesecretorypathway:L.CaroandG.Paladepancreatictissue（胰腺组织）culturingintheculturemediumaddingaminoacids(3H-Leu)byisotope（同位素）labelingpulse-chaseexperimentand胰腺 细豚鼠胰腺组yeastmutantsrelativewithendomembraneEndomembraneSystem(内膜系统ConceptsofEndomembraneComponentofEndomembraneEndoplasmicGolgicomplexCharacteristicsofendomembranesystemBiologicalsignificanceofendomembrane9TheconceptsofEndomembraneSystem:allmembrane-enclosedcompartmentsinthecytosol,whicharecorrelativeinstructure,functionandbiogenesis(生物发生)membrane,includingReticulum,Golgicomplex,lysosomesendosomes(胞内体或内体)andsecretoryvesicles(泡).Membrane-boundedorganelles:allorganelleswithmembranestructureinthecytosol.细胞膜、生物膜、细胞内膜系 1)EndoplasmicERdiscovery：Garnier(1897)-OpticalMicroscope:bar-like(条形)orsilk-likestructureincytoplasm--K.R.Porteretal(1945)—electronmicroscopemousefibroblast(成纤维细胞)cultured:endoplasmicregion(内质区)--anet-likelabyrinth(迷宫).(潴(潴泡面space胞质溶胶面ER：anetworkofbranchingtubulesandflattenedsacs（潴泡）---extendfromthenuclearmembranethroughoutthe ERisthelargestorganelleinmosteukaryoticcells.ERcisternalspaceoftenoccupiesabout10%ofthetotalcellvolume.ERmembranemayaccountforabouthalfofthetotalareaofallcellmembranes.TypesofendoplasmicRoughendoplasmicreticulum membrane-boundribosomesboundtoitscytosolicsurface.Smoothendoplasmicreticulum(SER)----branchingtubules,noSpecialtypesofsarcoplasmicreticulum(肌质网:心肌和骨骼肌microsome(微粒体):ERfragmentsresealtosmallclosedMicrosome(微粒体--proteinsynthesisandtranslocation,protein差速离Ca2+uptakeandrelease,and差速离ChemicalcomponentofER:proteins(60%),LipidsProteins:Glycoprotein(糖蛋白enzymesthecomponentofelectrontransportchain(电子传递链)suchasCytochromeP450------glucose-6-phosphatase–marker----thedistributionofERproteinsisheterogeneous(异质性ribophorin核糖体结合蛋白P450enzymes（SER标志酶）translocon（易位子）proteincomplex:Lipids：Phospholipids(PrincipallipidERFunctionofSynthesisandtransportofSecretoryproteins(antibodyhormones,extracellularmatrixcomponent(Glycoprotein（糖蛋白）)--integralmembraneproteinssuchas--Water-solubleproteinsforresidencewithin PolyribosomesarelocatedtoRER?1971Blobeletal(USA):signalsequence?ResearchofsignalMilstein等(1972)-cell-freesystem–synthesisofIgGlightchain:proteinssynthesizedmore20-aathanproteinsreleasedintothe G.Blobel等Invitroproteintranslationwithcell-freesystem:signalsequenceisexisting.Theroleofsignalsequence？？Transportdirectionofproteinssynthesizedon1960s，RedmanandSabatini,RER??whethernewlyproteinsenterRER进入ER嘌呤进入ER放射Secretaryprotein,synthesizesecretaryproteinswithpolyribosomesthenremoveERwithdetergent,continueproteinsynthesisyzeproteinproductscollectedatdifferenttimepointResults:theproductscollected:earlyorlateTransportwayofproteinssynthesizedbyHydrolysisexperimentusingproteinaseCell-freesystemaddingRERmicrosomes--synthesizesecretoryproteins，addingproteinaseCell-freesystem（RERmicrosomes)--synthesizesecretoryproteins，addingbothproteinaseanddetergentResults:proteinsaredegradated?co-translationtranslocation翻译):边合成 Signalpeptide（信号肽theaminoacidsequenceattheN-terminusofthenewlysynthesizingpolypeptidechain 15-35aminoacidresidues,N-terminuscontainingoneorseveralpositivelychargedresidues,followedby6-12hydrophobicresidues，directingpolypeptidechainstoERlumen（腔）.疏HIV-1 的糖蛋ThesignalsequencehasnospecificityforthepolypeptidechainguidedbyusingproteinlocalizationtechniquethesignalsequenceiscutafterthepolypeptidechainentersERlumenSeveralproteincomplexesbindingtoERmembrane(Walter,Blobel等1981）SRP（signalrecognitionparticle信号识别颗粒):recognisingandbindingtosignalsequencedirectingERSignaltothereceptorDP(dockingprotein,停泊蛋白):thereceptorlocatedonERtranslocon易位子SRP:a

rodlike 信号肽识合位点ribonucleoprotein(RNP)--sixdifferent--asmallRNAmolecule(300 s（功能域site(P54)▲translational▲SRPreceptorbinding

位DP:anintegralmembraneproteinheterodimer:hydrophilicαsubunitwithGTP-bindings,hydrophobicβsubunit(embeddedinRERSRPSRP-DP识别的GDP-GTP交换循translocon易位子SeveralcopiesoftheSec61complexassembleformacylindertransloconchannel(5～6nmhigh8.5 acentralaqueouspore,roughly2nm meter,theporeisadynamicgatedstructurethreetypesofSec61inmammals:α,βandSignalhypothesis（信号假说1975年，BlobelProteinstranslocatedbyERstartsynthesizingincytosolicfreeribosomes,thesignalpeptideattheN-terminusdeterminetheir WhentheERsignalpeptideemergesfromtheribosomes,SRPbindstothesignalpeptide,therebyinducingapauseintranslation.SRP–ribosomecomplexbindstotheSRPreceptor(DP).ThisinteractionbringstheSRP–ribosomecomplextoaproteinGTPhydrolysis，SRPisreleasedandtheproteintranslocatoropens，theribosomethenbindstothetranslocator，teinsynthesisresumes，thetranslocatortransfersthepolypeptidechainacrossthelipidbilayer,thepolypeptidechainentersERlumen，thesignalsequenceisthencleavedoffbyasignalpeptidaseintheERmembrane. proteinsynthesisends，thematureproteinisreleasedintotheERlumen.theproteintranslocatorisclosed，theribosomeleavesERmembrane. ProcessingandModificationofnewlysynthesizedproteinsinERN-linkedglycosylation(Asn-X-Theformationofdisulfidebondsbetweenthesidechainsofcysteineresidues:proteindisulfideisomerase(PDI-二硫键异构酶)Hydroxylation(ProN-Linked第一第一--doli