生物信息學(xué)分子生物學(xué)中心法則

1、會(huì)計(jì)學(xué)1生物信息學(xué)分子生物學(xué)中心法則生物信息學(xué)分子生物學(xué)中心法則ReplicationReplication，復(fù)制：在親代，復(fù)制：在親代DNADNA雙鏈的每一條鏈上按堿基雙鏈的每一條鏈上按堿基配對(duì)而準(zhǔn)確地形成一條新的配對(duì)而準(zhǔn)確地形成一條新的互補(bǔ)鏈，結(jié)果生成兩個(gè)與親互補(bǔ)鏈，結(jié)果生成兩個(gè)與親代鏈相同的代鏈相同的DNADNA雙鏈。雙鏈。在在DNA復(fù)制時(shí)，親代復(fù)制時(shí)，親代DNA的雙螺旋先解旋，然后以每條的雙螺旋先解旋，然后以每條鏈為模板，按照堿基配對(duì)原則，在這兩條鏈上各形成一條鏈為模板，按照堿基配對(duì)原則，在這兩條鏈上各形成一條互補(bǔ)鏈。在每一個(gè)新形成的雙螺旋中，一條鏈?zhǔn)菑挠H代互補(bǔ)鏈。在每一個(gè)新形成的雙螺

2、旋中，一條鏈?zhǔn)菑挠H代DNA來(lái)的，另一條是新形成的。來(lái)的，另一條是新形成的。355 33 5533553leading strand (synthesized continuously)lagging strand (synthesized discontinuously)Each replication fork has a leading and a lagging strand The leading and lagging strand arrows show the direction of DNA chain elongation in a 5 to 3 direction The

3、small DNA pieces on the lagging strand are calledOkazaki fragments (100-1000 bases in length)replication forkreplication forkRNA primer533535direction of leading strand synthesisdirection of lagging strand synthesisreplication fork5353Movement of the replication forkMovement of the replication forkR

4、NA primerOkazaki fragmentRNA primer5在DNA復(fù)制過(guò)程中，由眾多的酶和蛋白質(zhì)參與DNA的復(fù)制作用。復(fù)制體的基本活動(dòng)包括：1）雙鏈的解開(kāi)；2）RNA引物的合成；3）DNA鏈的延長(zhǎng)；4）切除RNA引物，填補(bǔ)缺口，連接DNA片段；5）切除和修復(fù)錯(cuò)配堿基。Transcription，轉(zhuǎn)錄：以DNA為模板，按堿基配對(duì)將其中所含的遺傳信息傳給RNA，形成一條與DNA鏈互補(bǔ)的mRNA鏈的過(guò)程。編碼鏈，有義鏈模板鏈，無(wú)義鏈1）RNA聚合酶與DNA模板的結(jié)合TranscriptionRNA polymerase,RNA聚合酶聚合酶closed promoter complex,

5、封閉的啟動(dòng)子復(fù)合物封閉的啟動(dòng)子復(fù)合物open promoter complex,開(kāi)放的啟動(dòng)子復(fù)合物開(kāi)放的啟動(dòng)子復(fù)合物initiationelongationterminationRNA productRNA chains are synthesized in a 5 to 3 directionProkaryotic RNA polymerase structureRNA polymerase of E. coli is a multisubunit proteinSubunitNumberRole a a 2uncertain b b 1forms phosphodiester bonds

6、b b 1binds DNA template s s 1recognizes promoter and facilitates initiationa a2 2bbbbs sa a2 2bbbb + s sholoenzyme core polymerase sigma factorRNA polymerase holoenzyme (+ s s factor) closed promoter complex (moderately stable) the sigma subunit binds to the -10 region once initiation takes place, R

7、NA polymerase does not need very high affinity for the promoter sigma factor dissociates from the core polymerase after a few elongation reactions elongation takes place with the core RNA polymerase open promoter complex (highly stable) the holoenzyme has very high affinity for promoter regions beca

8、use of sigma factors s sigma can re-bind other core enzymesThe sigma cycles ss s三聯(lián)體密碼子的特點(diǎn)：三聯(lián)體密碼子的特點(diǎn)：1）方向性）方向性2）無(wú)標(biāo)點(diǎn)性）無(wú)標(biāo)點(diǎn)性3）簡(jiǎn)并性）簡(jiǎn)并性4）通用性）通用性5）擺動(dòng)性）擺動(dòng)性起始密碼子：ATG。終止（無(wú)義）密碼子：UAAUGAUAG。同義密碼子：編碼同一個(gè)氨基酸的幾個(gè)密碼子。Translation，翻譯：在RNA控制下，根據(jù)核酸鏈上每三個(gè)核苷酸決定一個(gè)氨基酸的三聯(lián)體密碼規(guī)則，合成出具有特定氨基酸順序的蛋白質(zhì)肽鏈的過(guò)程。Protein Synthesis and Protein

9、 Processinga). RNA structureb). Protein synthesisi). Initiation of protein synthesisii). Peptide bond formation; peptidyl transferaseiii). Elongation and termination類(lèi)型結(jié)構(gòu)作用mRNA信使RNA單鏈；原核生物的mRNA為多順?lè)醋?，真核生物的為單順?lè)醋印NA原始遺傳信息的直接接受者；合成蛋白質(zhì)直接模板。tRNA轉(zhuǎn)運(yùn)RNA二級(jí)結(jié)構(gòu)是三葉草型結(jié)構(gòu)；三級(jí)結(jié)構(gòu)為倒L型結(jié)構(gòu)。轉(zhuǎn)運(yùn)氨基酸到核糖體上；通過(guò)反密碼子識(shí)別mRNA上的密碼子。rRNA

10、核糖體RNA16S (small ribosomal subunit)23S (large ribosomal subunit)5S (large ribosomal subunit)含量大，維持核糖體的空間結(jié)構(gòu)；使mRNA和tRNA結(jié)合在適當(dāng)位置；識(shí)別mRNA上的啟動(dòng)和終止信號(hào)。核糖體是蛋白質(zhì)生物合成的場(chǎng)所；核糖體是蛋白質(zhì)生物合成的場(chǎng)所；mRNAmRNA是合成的模板；是合成的模板；tRNAtRNA是模板與是模板與“合成原料合成原料”氨基酸之間的接合體。氨基酸之間的接合體。 原核生物的核糖體為70S，由50S和30S的大小亞基組成；真核生物的核糖體為80S，由60S和40S的大小亞基組成。rR

11、NA是構(gòu)成核糖體的骨架。是構(gòu)成核糖體的骨架。16S (small ribosomal subunit)23S (large ribosomal subunit)5S (large ribosomal subunit)Ribosome structureAP PPPPPPPP-sitepeptidyl tRNA siteA-siteaminoacyl tRNA sitemRNA5Small subunit(40S)Large subunit(60S)Ribosome with bound tRNAs and mRNAa.a. +tRNA+ATP氨酰-tRNA+AMP+PPi氨酰氨酰-tRNA合成

12、酶合成酶氨酰-tRNA合成酶能識(shí)別tRNA，并催化反應(yīng)。對(duì)L-氨基酸有極高的專(zhuān)一性，每種氨基酸都有一個(gè)專(zhuān)一的酶。氨酰-tRNA合成酶的高度專(zhuān)一性，防止在蛋白質(zhì)合成時(shí)錯(cuò)誤的氨基酸摻入多肽。Tertiary structureSecondary structuretRNA一個(gè)新生肽鏈的誕生，除了必須有mRNA模板，tRNA及核糖體外，還需要許多蛋白因子。如，起始因子(IF)，延長(zhǎng)因子(EF)和終止因子(RF)等的參與。肽鏈合成的方向是N-C,mRNA信號(hào)被轉(zhuǎn)譯的方向是5-3。mRNA5 cap40S subunitMeIF2AUGInitiator tRNA bound to thesmall r

13、ibosomal subunit with theeukaryotic initiation factor-2 (eIF2)Initiation of protein synthesis: mRNA bindingThe small subunit finds the 5 cap andscans down the mRNA to the first AUG codonmRNA5 40S subunitMeIF2AUG the initiation codon is recognized eIF2 dissociates from the complex the large ribosomal

14、 subunit binds60S subunitmRNA5 MAUG aminoacyl tRNA binds the A-site first peptide bond is formed initiation is completeGCCAmRNA5 MAUG GCCA氨酰-tRNA NH2 CH3-S-CH2-CH2-CH O=CPeptide bond formation peptide bond formation is catalyzed by peptidyl transferase(肽基轉(zhuǎn)移酶肽基轉(zhuǎn)移酶) peptide bond formation results in a

15、 shiftof the nascent peptide from the P-siteto the A-site NH2 CH3-S-CH2-CH2-CH O=C O tRNA NH2CH3-CH O=C O tRNANCP-siteA-site OH tRNA NHCH3-CH O=C O tRNAP-siteA-sitePUCAPPPPPUCA GCA GGG UAGAPPPPElongationGCA GGG UAG following peptide bond formationthe uncharged tRNA dissociatesfrom the P-site the rib

16、osome shifts one codon alongthe mRNA, moving peptidyl tRNAfrom the A-site to the P-site; thistranslocation requires theelongation factor EF2 the next aminoacyl tRNA thenbinds within the A-site; this tRNAbinding requires the elongationfactor EF1EF1EF2 energy for elongation is provided bythe hydrolysi

17、s of two GTPs: one for translocation one for aminoacyl tRNA bindingPUCA GCA GGG UAGPPPPTermination when translation reaches the stopcodon, a release factor (RF) bindswithin the A-site, recognizing thestop codon release factor catalyzes the hydrolysisof the completed polypeptide fromthe peptidyl tRNA

18、, and the entirecomplex dissociatesRFPUCA GCA GGG UAGPPPPPPP內(nèi)含子內(nèi)含子外顯子外顯子 遺傳功能的單位，它是一段編碼蛋白質(zhì)或RNA分子的DNA序列。 執(zhí)行生物功能的最重要的生物大分子之一，它是單鏈狀分子，由20種不同的氨基酸組成。DNADNARNAcDNA新生肽蛋白質(zhì)按基因編碼的信息在生物體內(nèi)合成蛋白質(zhì)的過(guò)程基因調(diào)控網(wǎng)絡(luò)基因調(diào)控網(wǎng)絡(luò)NU去折疊重折疊ReplicationReplication，復(fù)制：在親代，復(fù)制：在親代DNADNA雙鏈的每一條鏈上按堿基雙鏈的每一條鏈上按堿基配對(duì)而準(zhǔn)確地形成一條新的配對(duì)而準(zhǔn)確地形成一條新的互補(bǔ)鏈，結(jié)果生成兩個(gè)與親互補(bǔ)鏈，結(jié)果生成兩個(gè)與親代鏈相同的代鏈相同的DNADNA雙鏈。雙鏈。RNA polymerase holoenzyme (+ s s factor) closed promoter complex (moderately stable) the sigma subunit binds to the -10 region once initiation takes place, RNA polymerase does not nee