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Translation - Coggle Diagram

- - - - Start site = where ribosome attaches to mRNA and incorporates amino acids
      - Bacterial start site is approximately 10nt downstream of ribosome binding site
      - Eukaryotic start site is at the 5' cap
        
        ribosome scans before translating
- - - - MEMORIZE tRNA CLOVERLEAF STRUCTURE
  - - - discriminator region/acceptor arm
        
        3' end
        
        OH
        
        amino acid arm
        
        sequence = CAA
      - pseudouridine loop
      - variable loop - the size is what varies
      - Anticodon loop
        
        contains the anticodon (read from 5' to 3' just like codons so don't forget to flip the order on the test)
        
        Ex: Codon is AUG. Anticodon is therefore CAU.
      - D-loop
    - - mRNA has codon sequence
  - - - one for each amino acid
      - 1 aminoacyl tRNA synthetase recognizes all the tRNA's for one amino acid
      - Catalyzes two reactions
        
        adenylation
        
        amino acid + ATP -----> aminoacyl AMP
        
        diphosphate leaves
        
        tRNA charging
        
        Class I Reaction
        
        Enzyme = class I aminoacyl tRNA synthetase (aka: phe-tRNA synthetase)
        
        2' OH of uncharged tRNA attacks adenylated AA (aminoacyl AMP) at the carbonyl group and releases AMP
        
        Class II Reaction
        
        Enzyme = class II aminoacyl tRNA synthetase (aka: Gln-tRNA synthetase)
        
        3' OH of uncharged tRNA attacks adenylated amino acid (aminoacyl AMP) at the carbonyl group and releases AMP
      - Contact points to tRNA are the acceptor arm and near the anticodon loop
      - very good at proofreading to avoid mischarging
  - - - charged means to have an amino acid attached
- - - - Peptide bonding occurs in the large 50S subunit
        
        Peptidyltransferase rxn
        
        alpha amino group of A site attaches to carbonyl of P site
  - - - imitates EF-Tu-GTP but doesn't have RNA
        
        acts as an A site place holder until big scoot is complete
- - - - 70S = 50S + 30S
    - - 80S = 60S + 40S
    - - takes mass and shape into account
      - ultracentrifugation
  - - - eukaryotic = 5-10 aa's per sec
      - bacterial = 20 aa's per sec
- - - - If so, each ORF has its own RBS (Shine-Delgarno sequence)
  - - - cap scans mRNA until it finds the start codon (AUG)
- - - - f = formyl group
        
        formyl group speeds up translation
    - - This puts AUG at start site
  - - - 1) eIF1A blocks the tRNA at the A site. eIF1 prevents the 60S subunit from binding to the E site.
        
        No mRNA yet
      - 2) eIF2-GTP takes the initiator tRNA (Met-tRNAi^Met) to the the P site. eIF5B-GTP and eIF2-GTP stabilize initiator tRNA into the P site
        
        eIF2-GTP +eIF5b-GTP + initiator tRNA = 43S preinitiation complex
        
        Still no mRNA yet
      - 3) eIF4F binds to the 5' cap, brings the mRNA to the preinitiation complex (43S).
        
        RNA helicase (moves the eIF4F) + ATPase scans for the Kozak sequence
        
        Kozak sequence shows ribosome where to settle on mRNA sequence and begin translation
        
        PolyA Tail also binds at this step
        
        eIF4F sticks 5' cap to polyA tail to cause circularization
    - - Threading continues until the Met-tRNAi is at the P site.
    - - All eIF factors are released at this point
- - - - 1) RF (release factor) goes into the A site and causes a hydrolysis rxn on the polypeptide chain in the P site
        
        RF's are molecular mimics of tRNA's but the stop codons have a specific binding site for it
      - 2) The polypeptide chain is released from the ribosome. RF3-GDP binds to RF in the A site
      - 3) After GDP is exchanged for GTP on RF3 in the A site and RF leaves
      - 4) RF3- GTP gets hydrolyzed leading to RF3-GDP product that leaves the ribosome
    - - 1) RRF (ribosome recycling factor) binds to the A site
        
        RRF is also a tRNA mimic
      - 2) RRF recruits EF-G-GTP (the translocation factor from elongation + an additional phosphate)
      - 3) GTP hydrolysis (GTP-> GDP) moves uncharged tRNA to the E site and the RRF to the P stie. EF-G-GDP leaves the ribosome (and is ready for elongation step 3- hence recycled)
      - 4) RRF being in the P site leads to subunit disassociation. RRF leaves.
      - 5) IF-3 binds to small subunit to prevent re-sticking and initiation begins again.