蛋白質(zhì)分選下PPT課件

1、secretory pathway 第1頁/共34頁1.1 Synthesis and Targeting of Mitochondrial 線粒體具有1000多種蛋白質(zhì)，其自身合成的僅十余種，因此大量蛋白質(zhì)是在細(xì)胞質(zhì)中合成的。第2頁/共34頁 線粒體前體蛋白質(zhì)在在運輸以前，以未折疊的形式存在，N端有一段信號序列稱為導(dǎo)肽或引肽，完成轉(zhuǎn)運后被信號肽酶（signal peptidase）切除，就成為成熟蛋白，這種現(xiàn)象就叫做后轉(zhuǎn)譯（posttranslation）。信號肽的特點是： 多位于肽鏈的N端，由大約20個氨基酸構(gòu)成； 形成一個兩性螺旋，帶正電荷的氨基酸殘基和不帶電荷的疏水氨基酸殘基分別位于螺

2、旋的兩側(cè)； 對所牽引的蛋白質(zhì)沒有特異性要求。第3頁/共34頁MatrixOuter membraneIntermembrane spaceCross section of mitochondrionInner membrane第4頁/共34頁第5頁/共34頁Proteins Are Targeted to Sub-mitochondrial Compartments第6頁/共34頁 Protein import into mitochondria第7頁/共34頁Protein Transport into Inner Membrane and Intermembrane Space Requi

3、res Two Signal Sequences第8頁/共34頁線粒體轉(zhuǎn)運與葉綠體非常相似第9頁/共34頁1.2 Sort to Chloroplast Compartment第10頁/共34頁葉綠體蛋白轉(zhuǎn)運運輸機(jī)理與線粒體的相似。如： 都發(fā)生后轉(zhuǎn)譯； 每一種膜上有特定的轉(zhuǎn)位因子； 具有接觸點（contact site）； 需要能量，同樣利用ATP和質(zhì)子動力勢； 前體蛋白N端有信號序列，使用后被信號肽酶切除。 但兩者的蛋白質(zhì)轉(zhuǎn)運體系中除了某些hsp分子相同外，轉(zhuǎn)位因子復(fù)合體是不同的。第11頁/共34頁Import of rubisco small (S) subunits into the c

4、hloroplast stroma 轉(zhuǎn)運肽第12頁/共34頁內(nèi)囊體膜蛋白轉(zhuǎn)運需要兩段信號第13頁/共34頁1.3 Synthesis and Targeting of Peroxisome Proteins 核基因合成，后轉(zhuǎn)運方式運輸?shù)?4頁/共34頁C- and N-Terminal Targeting SequencesPTS1PTS2第15頁/共34頁第16頁/共34頁The nuclear pore complex第17頁/共34頁 Side view of nuclear pore第18頁/共34頁1.4.1Nuclear protein transport transport me

5、chanismmechanism nuclear localization signals ,NLSnuclear export signals, NESimportinexportin 第19頁/共34頁Mechanism of protein importProteins selected for import into nucleus have a nuclear localization signal (NLS) e.g.-Pro-Pro-Lys-Lys-Lys-Arg-NLS is recognized by cytosolic nuclear import receptors wh

6、ich bind to nuclear pore fibrils extending into cytosolPore opens and protein plus import receptor enter nucleus. Import receptor exported for re-use第20頁/共34頁Nuclear localization signals 第21頁/共34頁Nuclear localisation signal (NLS)第22頁/共34頁Nuclear localization signals 第23頁/共34頁第24頁/共34頁第25頁/共34頁Mechan

7、ism of transport through nuclear poresNLS need not cut after transport 第26頁/共34頁Nuclear importNuclear import第27頁/共34頁 Protein transport by nucleus pore complex Transport is selective Restrict transport particle Require energy expenditure saturated dynamic Transport is double direction Import and exp

8、ort 第28頁/共34頁1.4.2 Mechanism of export from nucleusMost of traffic moving out of nucleus consists of different types of RNA moleculesRNA moves through nuclear pore as complex of ribonucleoprotein (RNP):核糖核蛋白顆粒Protein component of RNP contains a nuclear export signal (NES) that is recognised by export proteinsmRNA is bound by hnRNP only after fully spliced so only mature RNA is exported第29頁/共34頁nuclear RNA and protein export mRNA export 核內(nèi)不均一核糖核蛋白核內(nèi)不均一核糖核蛋白 (heterogeneous ribonucleoprotein, hnRNP)信使信使RNP(messenger RNP, mRNP)mRNA的輸出的輸出nuclear pr