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Eukaryotic translation pathway
- 1. Eukaryotic translation SUKHVIR KAUR Ph.D. Biotechnology +M.Phil. Specialization: Molecular biology, yeast genetics, Translation Regulation
- 2. What is translation? The synthesis of protein molecules using mRNA as the template, in other word, to translate the nucleotide sequence of mRNA into the amino acid sequence of protein according to the genetic codon. DNA mRNA Protein Transcription Translation
- 3. 1 . Initiation 2 . Elongation 3 . Termination Steps of translation
- 4. 1. Initiation • Complex and large process Components: • It require 12 initiation factor ( eIF2, eIF3a, eIF1, eIF1A, eIF5, eIF4A, eIF4E,eIF4G, eIF4B, eIF5B, eIF2B, eIF6) • Met-tRNAi Met • mRNA • 40S small ribosome subunit
- 5. Steps of translation initiation 1.Formation of ternary complex (TC) :eIF2.GTP binds to initiator Met-tRNAi Met 2. Formation of 43S Pre -Initiation Complex (PIC):eIF1+eIF1A+eIF5+eIF3 initiation factors binds to 40S ribosome and help in recruitment of TC to 40S subunit of ribosome eIF2 Met-tRNAi Met 40S Met-tRNAi Met Alan G. Hinnebusch, 2017
- 6. Steps of translation initiation 3. Activation mRNA: mRNA activated by eIF4E+eIF4B+eIF4A+eIF4G initiation factors binds mRNA and prepare for its binding with 43S PIC Complex Alan G. Hinnebusch, 2017
- 7. Steps of translation initiation 4. mRNA binding with 43S complex : Activated mRNA binds to 43S pre initiation Complex makes it 43S -mRNA Complex. Alan G. Hinnebusch, 2017
- 8. Steps of translation initiation 5 Scanning of mRNA for start codon: 43S Pre initiation Complex Start scanning of mRNA for the search of AUG start codon and GTP bounded to eIF2 is hydrolyzed by eIF5 initiation factor. Alan G. Hinnebusch, 2017
- 9. Steps of translation initiation 6. AUG recognition: After recognition of AUG start codon by tRNA confirmation changes occur in complex and factor eIF1and Pi release form complex after that eIF5/eIF2- GDP dissociate from complex . eIF5B-GTP initiation factor binds to complex provide energy for the binding of 60S larger ribosome subunit. Alan G. Hinnebusch, 2017
- 10. Steps of translation initiation 7. 60S subunit joining: 60S subunit joins to complex and makes it 80 complex . eIF5B,eIF1A initiation factor release from complex. Alan G. Hinnebusch, 2017
- 11. 2.Elongation 1.STEP: eEF1α+GTP brought aminoacyle- tRNA to Ribosome empty A site binds according to next codon in mRNA eEF1α+GDP release from complex and again activated by elongation factor eEF1βγ 2. STEP: Polypeptide chain transfer from P site to new amino acid at A site and make peptide bond. 3 .STEP: eEF-2 induce translation of ribosome along the mRNA so that naked tRNA is ejected form E site and peptidyl-tRNA moves to P site leaving the A site empty and residing over the next codon of mRNA. This process is continue till a stop codon is encountered . Peptidyl transfer Step 2 Peptide bond formation Ribosome A site waiting for new aminoacyl tRNA Incoming aminoacyl- tRNA+eEF-1α Elongation cycle eEF1α+GDP release from complex GDP exchange factor eEF1βγ Translocation
- 12. 3.Termination 1 eRF1 (eukaryotic release factor) recognizes all stop codons (UAG,UAA,UGA). 2. Other eRF3 release factors bind to A site with bounded GTP and leads to peptidyl transferase activity and empty tRNA release from complex 3 inactive ribosome then releases its mRNA and dissociate itself into subunits.