1 / 29

Translation: From RNA to Protein

Translation: From RNA to Protein. Overall Picture. Protein. tRNA. To translate the mRNA transcript into a protein the codons must be read one at a time to assemble amino acids in the right sequence This occurs in the ribosome with the help of transfer RNA ( tRNA ). Structure of tRNA.

yardley
Download Presentation

Translation: From RNA to Protein

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Translation:From RNA to Protein

  2. Overall Picture Protein

  3. tRNA • To translate the mRNA transcript into a protein the codons must be read one at a time to assemble amino acids in the right sequence • This occurs in the ribosomewith the help of transfer RNA (tRNA)

  4. Structure of tRNA • Folded RNA molecule with an anticodonloop • anticodon contains nucleotide triplet which is complementary to mRNA codon; each codon codes for a specific amino acid • each tRNA carries a particular amino acid corresponding to its anticodon

  5. Structure of tRNA Ileu amino acid 3’ A tRNA molecule bound to an amino acid is called an amino - acyl tRNA ( aa-tRNA) 5’ anticodon

  6. Activation Enzymes • Ensure that the correct A.A. is attached to the tRNA

  7. Wobble • The cell only makes 30 - 45 tRNA molecules of the possible 64 because of the redundancy in the genetic code • “wobble” phenomenon The 3rd nucleotide in the anticodon is less important(binds weakly ; not specific)

  8. The Ribosome • A ribosome is a cluster of protein combined with ribosomal RNA (rRNA) • 2 subunits : small (40s) and large (60s) 3 binding sites for tRNA • P siteholds one aa - tRNA and the growing chain of amino acids • A sitereceives the tRNA with the next aa to be added to the chain • E sitereleases the tRNA back into the cytoplasm Large ribosomal subunit E P A Small ribosomal subunit

  9. Phases of Translation • Three phases • Initiation • Elongation • Termination

  10. Initiation • In the cytoplasm the ribosome attaches onto the mRNA at the 5’ cap. • A tRNA molecule with the start anticodon UAC (to complement the start codon AUG) binds to the mRNA - rRNA complex. The start tRNA carries the amino acid methionine • This complex then binds to the large ribosomal subunit

  11. C A A C G U G U G U U G U G A G U A P P P P P P P P P P P P P P P P P P S S S S S S S S S S S S S S S S S S Initiation 3’ 5’ E P A tRNA 5´ 3´

  12. Initiation

  13. Elongation The cycle of elongation has 3 steps: • aa-tRNA binds to the A site (aminoacyl site). • The large ribosomal subunit catalyzes the formation of a peptide bond with the previous amino acid. At the same time the polypeptide chain is passed from the tRNA in the P site (peptide site)to the tRNA in the A site. The ribosome moves along mRNA in 5’ 3’*ie. Translates in 5’ 3’ direction • Translocation:The ribosome moves 3 nucleotides (one codon) along the mRNA. This releases the used tRNA at the E site (exit site) and frees the A site for a new aa-tRNA to bind

  14. U U A G G U U A C G U G A G G C A U P P P P P P P P P P P P P P P P P P S S S S S S S S S S S S S S S S S S Elongation E P A 5´ 3´

  15. U U A G G U U A C G U G A G G C A U P P P P P P P P P P P P P P P P P P S S S S S S S S S S S S S S S S S S Elongation E P A 5´ 3´

  16. U U A G G U U A C G U G A G G C A U P P P P P P P P P P P P P P P P P P S S S S S S S S S S S S S S S S S S Elongation E P A 5´ 3´

  17. U U A G G U U A C G U G A G G C A U P P P P P P P P P P P P P P P P P P S S S S S S S S S S S S S S S S S S Elongation E P A 5´ 3´

  18. U G G U G C U U U A G U G A C G A A P P P P P P P P P P P P P P P P P P S S S S S S S S S S S S S S S S S S Elongation Growing polypeptide chain E P A 5´ 3´

  19. Elongation

  20. Termination I love protein • There is no tRNA with the complementary anticodon for the stop codon (UGA, UAG, UAA) • A protein release factor binds to the A site • This cleaves the polypeptide from the tRNAand breaks apart the ribosomal sub-units

  21. U G C U G U C U U A U G G C G A G A G C C A U U A C A P P P P P P P P P P P P P P P P P P P P P P P P P P P S S S S S S S S S S S S S S S S S S S S S S S S S S S Termination I’ll be back! protein E P A Release factor (protein) 3´ 5´ mRNA

  22. Termination

  23. 3D Shape • During translation polypeptides fold into a 3D shape • NOT DONE YET! Most newly synthesized proteins need modification in the ER and/or Golgi: After translation: • some amino acids may be removed • polypeptide can be divided into pieces • sugar and phosphate may be added • several polypeptides can join to form quaternary structure

  24. Polysome • One mRNA can be bound simultaneously to more than one ribosome. This is a polysome!(called a polyribosome in your textbook)

  25. Polysome

  26. Summary

  27. Homework Modelling Translation Activity – answer the questions provided.

  28. U G C U G G G A C A C G C U U G C C P P P P P P P P P P P P P P P P P P S S S S S S S S S S S S S S S S S S E P A 5´ 3´

More Related