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