Protein Synthesis

Ribosomes

16S rRNA Secondary Structures

30S Subunit Structure: 16S

rRNA & proteins

Electron Density Models of Both Subunits & tRNAs

70S Ribosome Showing tRNAs in A, P & E Sites

Prokaryotic Ribosomes

tRNA Structure

tRNA Structure

Modified Bases

Codon - Anticodon Base-Pairing - Role of

Wobble Bases

The Genetic Code

Aminoacyl Transferase Determines Specificity of Amino Acid Inserted at a

Codon

Aminoacyl-tRNA Synthetase Function

Aminoacyl tRNA Synthetase Structure

Chemistry of Aminoacylation

Roles of Eukaryotic Initiation FactorseIF-1

Promotes dissociation of 80S ribosomesBinds after eIF-4 and allows scanning

to begin

eIF-2GTPase activated by 60S subunit

bindingStabilizes binding of initiator met-

tRNAimet

eIF-3Promotes 80S ribosome dissociationBinds to 40S subunit & prevents

reassociation of 60S subunitPromotes binding of eIF-2

eIF-4Multi-component complexRecruits mRNA binding Recognizes cap, pA tailPromotes binding of eIF-1 for

scanning

eIF-5Promotes reformation of 80S ribosomeDisplaces eIF-6

eIF-6Promotes dissociation of 80S ribosomeBinds 60S subunit & prevents

reassociation with 40S subunit

Translation Initiation

eIF-1 + eIF-6

eIF-1 + eIF3

Steps in Eukaryotic Translation Initiation

eIF-6

eIF4 Complex Components & Functions

eIF4E – Cap bindingeIF4G – eIF3 binding PAB1P binding

eIF4A – helicaseeIF4B – stimulates RNA binding of eIF4A

Scanning Model of Eukaryotic Translation Initiation

Requirements: Must be able to determine which AUG is the right one to start translation

Kozack Consensus

CCRCCAUGG

Overview of Elongation

Elongation Step 1: Binding of aa-tRNA

Eukaryotic counterparts:EF1EF1

TC=EF1·GTP ·aa-tRNA

Kinetics of First Elongation Step Allow Proofreading

Rib = ribosome + met-tRNAimet

Peptidyl Transferase is Large Ribosomal Subunit

Peptidyl Transferase Active Site & Reaction Mechanism

GTP Hydrolysis Is Required for Translocation

Eukaryotic counterpart: EF-2

Structure of EF-G Compared to EF-Tu•tRNA Complex

EF-Tu•tRNAEF-G

Overview of Elongation

Elongation

Translocation

Similarity Between eRF1 Tertiary Structure and tRNA

Termination Factors RF-3 & eRF-2

RF-3 – ProkaryoticeRF-2 – Eukaryotic

Are GTPases that catalyzes the actual cleavage of the pep-tRNA bond to release the peptide

Protein Folding

Protein Folding