1 / 21

From Gene to Protein: Part 2 – Translation

From Gene to Protein: Part 2 – Translation. Making the Polypeptide Chapter 17C. “The human mind treats a new idea the same way the body treats a strange protein; it rejects it.” ~ P. B. Medawar. Nerdy Quote of the Day!. What is translation?. mRNA  Polypeptide

teresa
Download Presentation

From Gene to Protein: Part 2 – Translation

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. From Gene to Protein:Part 2 – Translation Making the Polypeptide Chapter 17C

  2. “The human mind treats a new idea the same way the body treats a strange protein; it rejects it.”~ P. B. Medawar Nerdy Quote of the Day!

  3. What is translation? • mRNA  Polypeptide • Occurs in cytoplasm on ribosome

  4. Ribosomal Structure • Large and small subunit – join to create active ribosome • Made in nucleolus • Made of rRNA and protein • 3 binding sites for tRNA • A-site: Aminoacyl-tRNA site • Holds tRNA carrying next aa to be added to chain • P-site: Peptidyl-tRNA site • Holds tRNA carrying growing polypeptide chain • E-site: Exit site • Discharged tRNAs leave ribosome

  5. Ribosomal Function • Synthesize proteins • Add amino acids together • Peptide bonds – carboxyl and amino ends

  6. tRNA Structure • Transfer RNA • Used repeatedly (about 45 different versions) • About 80 nucleotides long • Complement to mRNA (NOT identical!) • Folds on itself to form 3D structure using hydrogen attractions • “L” shaped • Anticodon end vs. aa End

  7. tRNA Function • Picks up designated aa and brings it to ribosome • Drops off, leaves, gets another • Interpreter of mRNA by codons

  8. Aminoacyl tRNA Synthetases • Enzyme that joins aa to tRNA • 20 different enzymes • 1 for each aa • Hydrolysis of ATP provides energy

  9. Steps to Translation • Initiation • Binding of ribosome, AUG • Elongation • Addition of more aa to polypeptide chains • Termination • Stop codons, release factors

  10. TRANSLATION: INITIATION • Small subunit + mRNA + special initiator tRNA • mRNA initiation codon AUG starts translation • Codes for Met and attaches to AUG • Large subunit can bind • Completes Translation Initiation Complex • **Various initiation factors are needed • **GTP required • Initiator tRNA moves to P-site • Leaves A-site open for next tRNA + aa

  11. Figure 17.17 The initiation of translation

  12. INITIATION Prokaryotes vs. Eukaryotes • In Prokaryotes • rRNA of small subunit base-pairs with mRNA leader • In Eukaryotes • 5’ cap tells small subunit to attach at 5’ end

  13. TRANSLATION: ELONGATION • Codon Recognition • mRNA in A site hydrogen attracts to anticodon of incoming tRNA+aa • Elongation factor helps tRNA into A-site • 2 GTP needed • Peptide Bond Formation • rRNA of lg. subunit acts as ribozyme • Peptide bond • Polypeptide separates from tRNA in P-site

  14. ELONGATION – Cont’d • Translocation • Moves tRNA A-site  P-site • tRNA/mRNA still hydrogen attracted • Next codon in A-site • P-site E-site, leaves ribosome • 1 GTP needed for release

  15. TRANSLATION: TERMINATION • Stop codon • UAA, UAG, or UGA • Do not code for aa • Release factor binds to stop codon in A-site • Adds H2O to chain • Hydrolysis of polypeptide from tRNA in P-site • Subunits dissemble and release factor leaves

  16. Figure 17.19 The termination of translation

  17. Post-Translational Modifications • Additions of sugars, lipids, phosphates, other • Chaperone protein • Help with folding 3º • Take off 1+ aa from N-terminus • Cleave by enzyme of 2+ pieces • Cut and are stuck together by disulfide bonds • 4º structure

  18. Polyribosomes • 1 mRNA gives rise to MANY polypeptide chains very quickly • Ribosomes line up one after another, making/using the same polypeptide

More Related