Genetic Code and Translation

Outline Concepts and Terms related to genetic code Translation Wobble Degeneracy isoaccepting Translation prokaryote eukaryotes

Amino Acid Transfer RNA ribosome

Genetic Code Table 1968 Wobble Degeneracy & mRNA

Isoaccepting & tRNAs Different tRNAs accept same amino acid!

We will focus our discussion of translation as a “Nonoverlapping Code” mRNA sequences

Animation of Prokaryotes Translation http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html

Steps of Translation 1. Binding of amino acids to tRNA 2. Initiation 3. Elongation 4. Termination 5. Peptide Release 6. Protein modification

Step 1 Binding of amino acid to tRNA

It takes two steps to “charge” the tRNA (proofreading activity) Aminoacyl-tRNA-synthetase Amino acid+ATP tRNA is charged

Up close view of “charged” tRNA

Step 2: Initiation of Translation Bacterial Initiation IF3

30S

Note 3 ribosomal sites E P A 70S E A

Eukaryotic Initiation Kozak Eukaryotic Initiation key differences

3. ELONGATION: look at the “EPA” sites Peptidyl transferase (ribozyme of large subunit)

Up close view of translation

Elongation continues on ribosomes

UAA UAG UGA Steps 4 and 5: Termination and Release

6. Lipoprotein Glycoprotein

Many antibiotics target prokaryotic translation.

Antibiotics and Translation Bind and block bacterial ribosomes “A” site Binds to large subunit; blocks peptide formation Blocks initiation step Blocks translocation step Tetracyclines Chloramphenicol Streptoymycin Erythromycin

Summary of important steps involved in translation For your review: Summary of important steps involved in translation

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6. Protein Modifications

Eukaryotic translation is very similar except: More IF’s Kozak sequence 5’CAP 3’poly-A tail