2. Protein Biosynthesis By Amr S. Moustafa, M.D.; Ph.D.

3. Components of Translation  Amino acids  The tRNA  Aminoacyl-tRNA synthetases  The mRNA  Competent ribosomes  Protein factors  ATP and GTP

4. Aminoacyl- tRNA Synthetases Activated amino acid Charged tRNA

5. Wobble Hypothesis

6. Competent Ribosomes

7. Protein Biosynthesis Translation: Genetic code on mRNA to amino acids on proteins Polycistronic Vs Monocistronic Steps: Initiation Elongation Termination Posttranslational modifications

8. Protein Biosynthesis: Initiation Complementarity: 5’-end mRNA and 3’-end 16S rRNA Shine-Dalgarno sequence

9. Protein Biosynthesis: Initiation-2 Initiation complex Assembly of components of translation: The mRNA 2 Ribosomal subunits Aminoacyl-tRNA GTP Initiation factors (IF or eIF)

10. Protein Biosynthesis: Initiation-3 Initiation codon AUG for metthionine Initiator tRNA: IF-2 and P-site N-Formylated methionine: Transformylase N 10 -formyl tetrahydrofolate After binding to tRNA Removal of N-formyl methionine

11. Protein Biosynthesis: Initiation-4 fMet-tRNA

12. Protein Biosynthesis: Elongation Addition of amino acids to the carboxyl end Elongation factors: EF-Tu, EF-Ts (eEF) Peptidyltransferase: 23S rRNA (ribozyme) and GTP Translocation: Ribosome moves in 5’-3’ on mRNA EF-G and GTP Movement of uncharged tRNA to E-site Movement of peptidyl-tRNA to P-site

13. Protein Biosynthesis: Termination Termination codons at the A-site RF-1: UAA and UAG RF-2: UAA and UGA RF-3: Binds GTP Termination: Release of newly synthesized polypeptide Dissociation of ribosome from mRNA Recycling: Ribosomal subunits mRNA and tRNA protein factors eRF: Single release factor Binds GTP

16. Peptide bond formation

17. Polyribosome: Several ribosomes and one mRNA