分子生物学第九章-蛋白质合成

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1、Chapter9ProteinsynthesisCodingregion编码区isapartofthegenethatrepresentsaproteinsequence.Codingstrand编码链ofDNAhasthesamesequenceasmRNA.templatestrand模板链ofdouble-strandedDNAistheonethatisusedtospecifythesequenceofacomplementarysinglestrandofRNA.(Thenon-templatestrandisidentica

2、linsequencetotheRNAproduct.)Transcription转录issynthesisofRNAonaDNAtemplate.Translation翻译issynthesisofproteinonthemRNAtemplate.IntroductionTranscriptiongeneratesanRNAwhichiscomplementarytotheDNAtemplatestrandandhasthesamesequenceastheDNAcodingstrand.Translationreadseachtrip

3、letofbasesintooneaminoacid.ThreeturnsoftheDNAdoublehelixcontain30bp,whichcidefor10aminoacids.Aminoacyl氨酰-tRNAistransferRNAcarryinganaminoacid;thecovalent共价linkageisbetweentheNH2groupoftheaminoacidandeitherthe3′-or2′-OHgroupoftheterminalbaseofthetRNA.Aminoacyl-tRNAsyntheta

4、sesareenzymesresponsibleforcovalentlylinkingaminoacidstothe2′-or3′-OHpositionoftRNA.Anticodon反密码子isatrinucleotide三核苷酸sequenceintRNAwhichiscomplementarytothecodoninmRNAandenablesthetRNAtoplacetheappropriateaminoacidinresponsetothecodon.Loop环isasingle-strandedregionofahairp

5、in发夹inRNA(orsingle-strandedDNA);correspondstothesequencebetweeninvertedrepeats反向重复induplexDNA.Stemisthebase-pairedsegmentofahairpin.TransferRNAistheadapterAtRNAhasthedualpropertiesofanadaptorthatrecognizesboththeaminoacidandcodon.Theadenosine腺苷at3’endiscovalentlylinkedtoa

6、naminoacid.TheanticodonbasepairswiththecodononmRNA.ThetRNAcloverleaf三叶草结构hasinvariant不变的andsemi-invariantbases,andaconserved保守的setofbasepairinginteractions.TransferRNAfoldsintoacompactL-shapedtertiarystructure三级结构withtheaminoacidatoneendandtheanticodonattheotherend.Aspace

7、-fillingmodelshowsthattRNAtertiarystructureiscompact紧密的.ThetwoviewsoftRNAarerotatedby90o.PhotographkindlyprovidedbyS.H.Kim.ThemeaningoftRNAisdeterminedbyitsanticodonandnotbyitsaminoacid.Aribosomeconsistsoftwosubunits亚基.MessengerRNAistranslatedbyribosomes核糖体Apolyribosome多核

8、糖体consistsofanmRNAbeingtranslatedsimultaneouslybyseveralribosomesmovinginthedirectionfrom5’-3’.E