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1、ProteinMetabolismProteinsynthesis--Translation?TheprocessinwhichthegeneticinformationpresentinanmRNAmoleculespecifiesthesequenceofaminoacidsduringproteinsynthesis.以mRNA為直接模板,tRNA為氨基酸運(yùn)載體,核蛋白體為裝配場(chǎng)所,共同協(xié)調(diào)完成蛋白質(zhì)生物合成的過(guò)程。也就是把mRNA的堿基排列順序轉(zhuǎn)譯成多肽鏈中氨基酸的排列順序。Threemajoradvancessetthestageforourpresentknowledge
2、ofproteinbiosynthesis?Thesiteofproteinsynthesis:ribosomes?Aminoacidareactivatedasaminoacyl-tRNA?ThegeneticcodeContents1.Thegeneticcode2.Proteinsynthesis3.Proteintargetinganddegradation1.ThegeneticcodeThegeneticcodewascrackedusingartificialmRNAtemplates?Acodonisatripletofnucleotidesthatcodesfora
3、specificaminoacid.?Nopunctuationbetweencodons?Initiationcodon:AUG?Terminationcodons(stopcodons,nonsensecodons):UAA,UAG,UGAReadingframeandOpenreadingframe?Areadingframeisacontiguous(鄰近的)andnonoverlappingsetofthree-nucleotidecodonsinDNAorRNA.Thereare3possiblereadingframesinastrand.Areadingframeth
4、atcontainsastartcodonandastopcodoniscalledanopenreadingframe.Featuresofgeneticcode?commaless(連續(xù)性)?nonoverlapping(讀碼不重疊)?Universal(通用性)?Degenerate(簡(jiǎn)并性)?Wobble(擺動(dòng)性)CodonandanticodonwobbleWobbleallowssometRNAtorecognizemorethanonecodon?Significance?Balancetherequirementsforaccuracyandspeed.密碼子的特性?
5、無(wú)標(biāo)點(diǎn)符號(hào)、讀碼不重疊、一定的防突變功能…AUGAAUAGAGAAGGCCGUC但如果是密碼子甲天酪精谷賴(lài)甘丙…第三個(gè)堿基改變,硫冬氨氨氨氨氨氨氨酰酸酸酸酸酸酸氨基酸有可能不酸胺變。簡(jiǎn)并性、擺動(dòng)性一個(gè)堿基突變,會(huì)如何?堿基丟失后續(xù)全變U一個(gè)堿基突變一個(gè)氨基酸改變TranslationalframeshiftingandRNAeditingSomemRNAsareeditedbeforetranslationRNAeditingofthetranscriptofthecytochromeoxidasesubunitIIgenefrommitochondriaofTrypanosomab
6、ruceiRNAeditingofthetranscriptofthegenefortheapo-lipoproteinB-100componentoflow-densitylipoproteinOverlappinggeneindifferentreadingframesarefoundinsomeviralDNAsGeneswithingenes.thecircularDNAofφX174Note:nonoverlappingincodonsPortionofthenucleotidesequenceofthemRNAtranscriptofgeneC,A,andKofφX174
7、2.Proteinsynthesis?Proteinsynthesistakesplaceintheribosome?TheribosomeisacomplexsupermolecularmachineBacterialribosomescontainsabout65%rRNAandabout35%proteinStructureofthebacterialribosome.greenrope:mRNA;shadesofgreen:tRNA?TherRNA