Chapter 4
Gene Translation: RNA → Protein
4.1 Translation System
1. Genetic codon
Degeneracy
Generality
Particularity
Codon
Anticodon
Wobble hypothesis
2. mRNA structure
mRNA structure of prokaryotes
polycistron
Shine-Dalgarno sequence
mRNA structure of eukaryotes single cistron 5’-cap 3’-poly(A)
3. tRNA
Extra arm
Acceptor arm
Anticodon loop
D loop TψCG loop
cloverleaf structure
tertiary structure
Upside-down “L”( 倒 L 形 )
size of
ribosome
Size of
subunits
Ratio
(RNA : protein)
prokaryotes 70S 50S, 30S 2 : 1
mammalian 80S 60S, 40S 3 : 2
5. Ribosome
4.2 Protein Synthesis in ProkaryotesInitiation1 、 Ribosome 30S subunit2 、 template mRNA3 、 fMet-tRNAfMet
4 、 IF-1, IF-2, IF-35 、 GTP6 、 Ribosome 50S subunit7 、 Mg2 +
Initiation
Elongation
aa-tRNA →A site
Formation of Peptide Bond
Translocation
Elongation of peptide chain
RE1, RF2, or RF3
Termination of translation
Peptide chain released
Animation
4.3 Protein Synthesis in Eukaryotes
Initiation
Processing of Nascent Protein
Removing fMet or Met
Formation of S-S bond
Chemical modification of amino acid
Intein splicing
The Mechanism of Protein Splicing
1. Functions of Chaperones
4.4 Molecular Chaperone
2. Main Types of Chaperones
molecular chaperone
chaperonin
trigger factor
Chaperonins
Trigger Factor in E. coli
4.5 Transmembrane Transport of Protein
Signal Hypothesis
Signal peptide,
SRP
DP
Signal peptidase
Model for the translocation of proteins into the endoplasmic reticulum in eukaryotes
(1) Components of Ubiquitin
4.6 Protein Degradation
1. Ubiquitin
(2) Ubiquitination
2. Proteasomes
3. Protein Degradation Pathways
(1) Ubiquitin-dependent degradation
(2) Ubiquitin-independent degradation
Summary
1. Structure of tRNA and ribosome
2. Procedures of protein translation
3. Differences between prokaryotic and
eukaryotic translation
4. What is the function of intein splicing?
5. Types of molecular chaperone and their functions
6. What is signal peptide? What is signal hypothesis?
7. Ubiquitin and mechanism of protein degradation