Module 4 Section 5 Flashcards

1
Q

Elongation: delivery of charged tRNA to prokaryotic decoding center steps

A
  1. Charged tRNA delivered to A-site by EF-Tu-GTP (elongation factor thermo unstable)
  2. A1492 and A1493 (adenosine) ‘flip out’ in response to the correct codon-anticodon BP
  3. causes conformational changes to the 30S subunit
  4. EF-Tu-GTP hydrolyzed to EF-Tu-GDP
  5. tRNA rotates into position (accomodation)
    EF-Tu is eEF1alpha in eukaryotes
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2
Q

Elongation: Peptidyl transferase rxn

A
  • peptide bond is formed between 2 AA bound by their tRNAs to the A and P sites on the ribosome
    1. alpha-amino group of amino-acyl tRNA in the A site attacks the carbonyl carbon of the ester bond linking the peptide to the tRNA in the P-site
  • alpha-amino is nucleophile
    2. growing chain is transferred to the tRNA in the A site
  • as ribosome shifts along mRNA, uncharged tRNA now moves to the E site and the peptidyl-tRNA moves to the P-site
  • this frees A site to bind next tRNA
  • peptidyl transferase is the enzyme that catalyzes the peptide bond formation
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3
Q

Aminoglyceride antibiotics

A
  • cause inappropriate flipping of the A1492/3 for non-cognate tRNAs
  • used to kill bacteria through translational fidelity (misfolded proteins = death)
  • at high doses, can cause read through of nonsense mutations in eukaryotes
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4
Q

Puromycin antibiotic

A
  • inhibitory antibiotic
  • structure is very similar to the 3’ end of an aminoacyl-tRNA
  • fits into peptidyl transferase center
  • not bound to the ribosome by interactions with 16S rRNA
  • if bound to chain, the peptide dissociates b’c the puromycin is not bound to the ribosome
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