Translation Dr. Kevin Ahern

Central Dogma

mRNA Structure Bacteria

Universal Redundant Logical Punctuated 64 Codons 3 Stops 1 Start Genetic Code Universal Redundant Logical Punctuated 64 Codons 3 Stops 1 Start 2 Unique for AA 59 Redundant

Translation Steps

Central Dogma Nucleus Cytoplasm Eukaryotes

Translation

Simple View of Translation Stop Codon Start Codon

Structure

tRNAs - Translator Molecules Amino Acid Attachment Point

tRNAs - Translator Molecules

Amino Acid Activation - Charging of tRNAs Aminoacyl tRNA-synthetase Type 1 - AA on 2’ OH Type 2 - AA on 3’ OH

“Charging” of tRNAs

fMet Synthesis in Prokaryotes

Wobble Base

Wobble Base

Small Ribosomal Subunit (30S Prokaryotes)

Large Ribosomal Subunit (50S Prokaryotes)

Structure 50S Ribosomal Subunit

rRNAs

Simple Overview

Overview

Prokaryotes - Shine-Dalgarno Sequence

Shine-Dalgarno Sequence 16S rRNA Sequence

Initiation

Initiation

Structure Protection Against Hydrolysis EF-Tu

Elongation

Elongation

Termination

Translation in Prokaryotes 1. Binding of mRNA by small subunit 2. Sliding to identify start codon (Shine-Dalgarno) 3. Base pairing of anticodon of initiator tRNA to AUG in mRNA (3 IFs) 4. Binding of large subunit 5. Entry of second tRNA into A-site (EF-Tu) 6. Peptide bond formation - peptide on tRNA in A-site 7. Translocation (requires GTP & EFG) 8. Exit of used tRNA, entry of new charged tRNA 9. Repeat 5-8 to STOP Codon 10. Entry of release factor with water

Translation in Eukaryotes Differences 1. mRNA structure 2. Ribosome sizes (60S & 40S) 3. rRNA sizes (extra rRNA) 4. No Shine-Dalgarno 5. No fMet

Translation in Eukaryotes - Initiation Kozak Sequences

Eukaryotic Translation

Elongation

Eukaryotic Translation Bonding to mRNA Premature Stopping of Translation Degradation of mRNA

Membrane Proteins

Structure

Membrane Protein Synthesis