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Translation

Translation. How the Genetic Information Is Used to Build a Protein. transcription. initial transcript RNA. processing. mature RNA. translation. Protein. Information Flow From DNA. replication. DNA. Properties of the Genetic Code. Triplet 3 nucleotides code for 1 amino acid

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Translation

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  1. Translation How the Genetic Information Is Used to Build a Protein

  2. transcription initial transcript RNA processing mature RNA translation Protein Information Flow From DNA replication DNA

  3. Properties of the Genetic Code • Triplet • 3 nucleotides code for 1 amino acid • Non-overlapping • Codons are adjacent to each other • Degenerate • Some amino acids have more than one codon • “Almost” universal • A few exceptions occur in mitochondrial, bacterial and protist genes

  4. 5’3’ Sequence of CODONS

  5. Accurate Protein Synthesis Depends on Codon-Anticodon Recognition

  6. tRNA Charging • A specific tRNA synthetase catalyzes the attachment of the appropriate amino acid to each tRNA • Energy from conversion of ATP to AMP drives the reaction

  7. Overview of Translation At the ribosome, codons in mRNA are recognized by tRNA anticodons to place amino acids in the specific sequence determined by the DNA. Three Stages of Translation: Initiation- assemble components to start process Elongation- add amino acids in repeated cycles Termination- release protein product

  8. Initiation (Prokaryotic) Formation of initiation complex containing: Small ribosomal subunit mRNA Initiator (f-Met) tRNA Large ribosomal subunit f-met UAC 5’-------------AUGUUUCUCUGA---3’ mRNA

  9. Elongation a. next tRNA binds to mRNA at the A site E site P site A site f-met phe UAC AAA 5’ -------------AUGUUUCUCUGA---3’ mRNA

  10. peptide bond Elongation b. amino acids are joined with peptidyl transferase f-met phe UAC AAA 5’-------------AUGUUUCUCUGA---3’ mRNA

  11. Elongation c. ribosome moves by one codon (translocation) --growing peptide is now in P site --first tRNA is in E site f-met phe UAC AAA 5’-------------AUGUUUCUCUGA---3’ mRNA

  12. Elongation d. first tRNA is released from E site f-met phe UAC AAA 5’-------------AUGUUUCUCUGA---3’ mRNA

  13. Elongation (second cycle) a. next tRNA binds to mRNA at the A site f-met phe leu UAC AAA GAG 5’ -------------AUGUUUCUCUGA---3’ mRNA

  14. peptide bond Elongation (second cycle) b. amino acids are joined with peptidyl transferase f-met UAC phe leu AAA GAG 5’ -------------AUGUUUCUCUGA---3’ mRNA

  15. Elongation (second cycle) c. ribosome moves by one codon --growing peptide is now in P site --second tRNA is now in E site UAC f-met phe leu AAA GAG 5’-------------AUGUUUCUCUGA---3’ mRNA

  16. Elongation (second cycle) d. second tRNA is released from E site UAC f-met phe leu AAA GAG 5’-------------AUGUUUCUCUGA---3’ mRNA

  17. Termination a. release factor binds to stop codon UAC f-met phe leu RF AAA GAG 5’-------------AUGUUUCUCUGA---3’ mRNA

  18. Termination b. protein chain is released other components separate f-met Large Subunit phe leu UAC RF GAG Small Subunit AAA 5’-------------AUGUUUCUCUGA---3’ mRNA

  19. Applying Your Knowledge If the mRNA sequence for codons 5, 6, and 7 of a protein is 5’-AAG-AUU-GGA-3’, what is the amino acid sequence in the protein? • Gly-ile-lys • Arg-leu-glu • Glu-leu-arg • Asn-met-gly • Lys-ile-gly

  20. IF-3 = Initiation Factor 3 Control of Initiation in Prokaryotes • Small Ribosomal Subunit binds to mRNA • IF-3 binds to small ribosomal subunit • Small ribosomal subunit binds to Shine-Dalgarno sequence on mRNA A sequence in the 16S rRNA of the small ribosomal subunit is complementary to the Shine-Dalgarno sequence on mRNA

  21. Formyl-methionine tRNA binds to mRNA • IF-2 +GTP + f-met-tRNA join • f-met-tRNA binds to the first codon • IF-1 joins to small subunit • IFs dissociate, GTP is hydrolyzed to GDP • Large Ribosomal Subunit binds to mRNA Control of Initiation in Prokaryotes

  22. Binding of Small Subunit assisted by proteins bound to -5’-methyl guanine cap -Poly-A tail Control of Initiation in Eukaryotes

  23. Control of Elongation by Elongation Factors EF-Tu joins GTP and a charged tRNA to form a complex that binds to the A site EF-Ts regenerates the EF-Tu + GTP complex EF-G and GTP are required for ribosome translocation

  24. Control of Termination by Release Factors RF3 forms a complex with GTP that binds to the ribosome RF1 binds to UAA and UAG RF2 binds to UAA and UGA

  25. Energetics of Translation

  26. Energetics of Translation How many phosphate bonds are required to build a protein of 100 amino acids?

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