第十一章 蛋白质的生物合成— 翻译 - gsau

1 TRNA RNA tRNA rRNA mRNA tRNA , tRNA AA tRNA tRNA anticodon codon mRNA mRNA 5 3 1 mRNA mRNA mRNA 5 3 Poly A AUGUAAAAAAA mRNA AUGUAA5 3 AUGUAA mRNA mRNA mRNA Eukaryotic mRNAP rokaryotic mRNA2 tRNA mRNA tRNA mRNA 20 tRNA aa-tRNAtRNA 1964 Holly. R. tRNAphe 77 NT 5 4 a aa accept arm tRNA 5 3 - 3 CCA A 3 2 -OH b D DHU D (anti codon arm) extra arm T C T C c 70 3.

2 T C DHU aa L L ---T C loop & DHU loop L L --- L wobble base L tRNA tRNA tRNA mRNA tRNA tRNA tRNA tRNA Prok fMet Euk Met tRNA: tRNA tRNA tRNA tRNA 3 tRNA -tRNA mRNA tRNA tRNA mRNA UAG mRNA tRNA mRNA5 -UAG-3 tRNA 3 -AUC-5 3 -AUG-5 mRNA 5 -UAC-3 Tyr Tyr4 Prok.

3 Protein 10 RNA RNA 80 Euk Size comparisons show that the ribosome is large enough to bind tRNAs and are large ribo-nucleoprotein particles that contain more RNA than protein and dissociate into large and small subunits. 30S 50S RNP RNA mRNA 30 RNA N-C 1 -tRNA tRNA mRNA tRNA AA AA tRNA AARS AA tRNAATP aabinding site tRNAbinding site ATP site AA + tRNA+ ATP AA tRNA+ AMP + ppiAARS 2 mRNA mRNA a 5 300 NT leader b AUG GUG UUG c AUG S D S D Shine-Dalgarno sequence AUG 4 ~13 NT 3 ~9 NT AGGAGG

4 3 IF IF: : mRNA aa-RNA 3 IF IF1IF2IF3 GTP 30S+50S+mRNA+fMet-tRNAf [70S mRNA fMet-tRNAf]+GDP+PiGTPIF-1 IF-2 IF-3 IF-3 30S 30S mRNA IF-1 30S A -tRNA 30S 50S IF-2 tRNA GTP Initiation requires factors and free subunits mRNA aa--tRNA (1)30S mRNA 30S---IF3+ mRNA30S IF3 mRNA 30S IF3+ 30S 30S mRNA SD 16S rRNA 3 SD IF3 30S 50S 30S codon P fMet tRNAMetf (2) tRNA IF2+ fMet---tRNAf IF2---fMet---tRNAf 30S---IF3---mRNA 30S---IF3---mRNA---IF2---fMet---tRNAf--- GTP IF2 tRNA GTP 3 70S a IF3 30S---IF3---mRNA---IF2---fMet---tRNAf--- GTP 50S IF3 50S b 70S 50S IF2 GTP GTP IF1 GTP 30S---mRNA---fMet---tRNA---50S IF2---fMet---tRNAf Euk Met tRNAi AUG eIF 2 eIF-4F Eukaryotic initiation uses several complexesThey act at all stages of the process, including 5 stages.

5 1) forming a complex with Met-tRNAi2) forming an initiation complex with the 5` end of mRNA 3)binding the mRNA-factor complex to the Met-tRNAi-factor complex 4)enabling the ribosome to scan mRNA from the 5` end to the first AUG 5)mediating joining of the 60S (A) stimulates the formation of an initiation complex at the 5 end. 70S80S 50S 30S60S 40S tRNAfMet-tRNAfMetMet-tRNAiMet 3 7 1 30S mRNA1) 40S Met-tRNAiMet2 30S mRNA fMet-tRNAfMet2)40S Met-tRNAiMet mRNA3 70S mRNA fMet-tRNAfMet3 80S mRNA Met-tRNAiMet 5 mRNA AA-tRNA A tRNA P tRNA E mRNA 30S P tRNA A tRNA tRNA E Prok tRNA 70S A 1 aa-tRNA 1 EF Tu--GTP+ --tRNA EF Tu + GTP 2 A P tRNA tRNA EF-Tu GTP EF Tu GDP 3 Ts Tu Ts EF Ts EF Tu GDP EF Tu GTP -----EF Tu GDP tRNA EF Tu GDPEF--TsEF Tu EF--TsGTP EF Tu--GTP 2 1 peptidyl transferase

6 23S rRNA 5S rRNA 2 tRNA P A tRNA AA 3 translocation mRNA 1 GTP EF G a EF G GTP ------- GTP GTP --------A P P tRNA E mRNA b EF G GDP fusidic acid c EF G Elongation 3 2 GTP mRNA 3 EF G GTP EF Tu tRNA A EF G tRNA EF--Tu A P tRNA A EF G GTP .. A P tRNA Prok Euk UAA UAG UGA RF Prok RF1 ---- UAA UAG RF2 ---- UAA UGA RF3 ---- RF1 RF2 Euk eRF----- UAA A GTP RF1 UAA A P tRNA GTP 70S 30S 50S mRNA mRNA mRNA 1 mRNA5 3 5 3 poly A mRNA 5 2 mRNA poly A poly A poly A 5 3 3 eIF-4F

7 EIF-2 4 UAA UGA UAG AA molecular chaperone .. 70 stress-70 chaperonin Hsp70 heat shock protein , Hsp70 --- In (rough endoplasmic reticulum RER) In Prok. --- inner membrane periplasm 1 N : N 15 30 AA 1 10aa 15 20aa15 30 aa1 3 aa Arg+, Lys+ ----- Phe, Leu, signal S.

8 , helix,--- --- Signal S. 2 1 a signal recognition particle SRP SRP RNA 7SL RNA 6 b SRP SSR docking protein c SRP GTP 70 AA 2 a b c 3 N fMet/Met S-D tRNA Prok.

9 Prok. Prok. Euk. Prok. Prok. Euk.