前体蛋白与叶绿体外表面结合ppt.ppt

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1、structureandfunctionofproteintransportmachineriesinchloroplasts左冰峰杨洋06/11/7chloroplastsThechloroplastsisanognanelleofprokaryoticoriginthatissituatedinaneukaryoticcellularenvironment.chloroplastsSixsubcompartments:AninnerenvelopemembraneAnouterenvelopemembraneInter

2、membranespaceStromaThylakiodmembraneThylakiodlumenproteintransportmechanismsThetwostypes:⑴Importofnuclear-encodedproteinsintothechloroplaststromathroughenvelopemembrane⑵proteintransportintothylakiodlumenacrossthethylakoidmembraneImportofproteinsintothechloroplasts

3、tromaProcess:Ⅰ.前体蛋白与叶绿体外表面结合:前体蛋白N端的转运肽(transitpeptides)和叶绿体外表面蛋白转运复合体上受体的相互作用;需少量ATP.Ⅱ.转运的早期阶段:在GTP或低浓度的ATP存在下,前体蛋白与蛋白转运复合体(translocationcomplexes)紧密结合.Ⅲ.转运末期:前体蛋白穿膜转运进入叶绿体基质,在分子伴侣(cytosolicchaperone)的协助下加工成为成熟的蛋白.transitpeptides(转运肽)Generalfeatures:ahighcontenti

4、nhydroxylatedresidues;analmostcompletelackofacidicresidues;anoverallhydrophilicnature.anumberoftransitpeptidesphosphorylationinthecytosolcouldsupporttheirassociationwithguidancecomplexes.transitpeptides(转运肽)Structure:transitpeptidecontainsthreeparts:⑴N端含非极性氨基酸残基——

5、参与前体蛋白与受体的结合。⑵中间段富含羟基和带正电荷的氨基酸残基——参与前体蛋白的精确定位。⑶C端形成双极性的β折叠——与转运后转运肽准确切割有关。transitpeptides(转运肽)Thegeneralfounction:⑴targettheproteintochloroplast⑵itprovidesan“address”thatlocatizesthepolypeptidetooneofthesubcompartments.☆Afterreachingtheorganellestroma,theyareremov

6、edbyastromalprocessingpeptidase(SPP)cytosolicchaperone14-3-3proteinsandHsp70在蛋白转运前,对前体蛋白进行解折叠,使其从杂的空间结构变成线型结构,以便于进行穿膜输;进入叶绿体的蛋白质,又在监护蛋白的作用下重新恢复其空间构象并实施其功能.translocationcomplexes◆theyareoligomericproteincomplexes.◆theyaredividedintoToccomplexandTiccomplex.◆Itisinit

7、iatedbyenergy-independentbindingoftheprecursorproteintosurfaceexposedreceptorsfollowedbyGTP-andATPdependentpartialtranslocationacrosstheouterenvelopemembrane.translocationcomplexesToccomplexs:theToccomplexwhichwasfirstisolatedfrompeachloroplastsconsistsofthreeprot

8、einsthataredesignatedaccordingtotheirmolecularweightasToc34,Toc75,andtoc159.ImportofproteinsintothechloroplaststromaToc34andToc159arereceptorproteinstha