Chapter 30. Protein Synthesis

Chapter 30. Protein Synthesis

(=Translation)

Cheju National Univ.

Department of Chemistry

Moon Eun-Sung

List of pregentation

1. Overview of the Gene Expression 2. Properties of The Genetic Code 3. Binding specificity of tRNA

4. Importance of Wobble theory in translation 5. Elongation mechanism in Translation

6. Translation mechanism in Eukaryotes

7. Summary

Overview of the Gene Expression

Molecular Cell Biology (by Lodish et al, 5e) p.11

Figure 1.11 The coded information in DNA is converted into the amino acid sequences of proteins by a multistep process

( 동영상 보기 ) - Transcription - Translation

Properties of the Genetic code_1

1. Nonvoerlapping 2. Comma less

3. Triplet code 4. Universal code 5. Degeneracy code

Lehninger Principle of Biochemistry (by D.L.Nelson et al, 4e) p.1038 Figure 27.7 "Dictionary" of amino acid code words in mRNAs.

Properties of the Genetic code_2

1. Nonoverlapping

- Reading frame

: 3 cases per 1 strand

- Only one possible

: from initiation codon

1. Molecular Biology of The Cell (by Alberts et al, 5e) p.368

- Figure 6.51 The three possible reading frames in protein synthesis.

2. Biology Workbench(San Diego Supercomputer center) - Analyze a Nucleotide sequence for Restriction Enzyme Sites

Properties of the Genetic code_3

2. Comma less

- Comma make the polymorphism of reading frame &

untranslation region

Figure 12.2(b) A continuous versus a punctuated code.

Properties of the Genetic code_4

3. Triplet code

- (a) : poly(UC) : contains only two codon

- (b) : poly(UUC) : contains only three codon - (c) : poly(UAUC) : contains variable codon

Molecular Biology (by R.F. Weaver et al, 3e) p.589

Figure 18.4 Coding properties of several synthetic mRNAs.

Properties of the Genetic code_5

4. The (Almost) Universal code

- from bacteria to human, were share the same code!

- rarely, have exception!

→ mitochondria, nuclei

Properties of the Genetic code_6

5. Degeneracy - related wobble theory - by the wobble

position, same a.a-tRNA to pair with more than one codon

1. Molecular Biology of The Cell (by Alberts et al, 5e) p.367 - Figure 6.50 The genetic code

2. Lehninger Principle of Biochemistry (by D.L.Nelson et al, 4e) p.1039 - Table 27.3 Degeneracy of the Genetic code

Binding specificity of tRNA_1

Molecular Biology of The Cell (by Alberts et al, 5e) p.368 Figure 6.52 A tRNA molecule.

Binding specificity of tRNA_2

Step1

: aminoacyl-tRNA synthetase Step2

: codon – anticodon form base pairs

Molecular Biology of The Cell (by Alberts et al, 5e) p.372

Figure 6.58 The genetic code is translated by means of two adaptors that act one after another

Importance of

Wobble theory in translation

Wobble position

→ 5’-first anticodon / 5’-third codon

reduces the number of tRNAs required to translate the genetic code

it make be ribosome structural difference between bacteria and eukaryotes

Phenylalanine codon – UUC/UUU Leucine codon – UUA/UUG

1. Molecular Biology of The Cell (by Alberts et al, 5e) p.369

- Figure 6.53 Wobble base-paring between codons and anticodons 2. Molecular Biology (by R.F. Weaver et al, 3e) p.592

- Figure 18.8 The wobble position

Elongation mechanism

in Translation_1

1. Molecular Biology of The Cell (by Alberts et al, 5e) p.374

- Figure 6.63 A comparison of procaryotic and eucaryotic ribosomes 2. Lehninger Principle of Biochemistry (by D.L.Nelson et al, 4e) p.1047

- Figure 27.9(d) Ribosomes

Elongation mechanism

in Translation_2

1. Molecular Biology of The Cell (by Alberts et al, 5e) p.375 - Figure 6.64 The RNA-binding sites in the ribosomes 2.Molecular Cell Biology (by Lodish et al, 5e) p.137

- Figure 4.27 Termination of translation in uekaryotes

Elongation mechanism

in Translation_2

<key point>

→ P

site

→ A

site

→ EF

-Tu

→ EF

-Ts

→ EF

-G

→ GTP

→ Peptidyl transferase

1. Molecular Biology (by R.F. Weaver et al, 3e) p.595 - Figure 18.10 Elongation in translation

2. Molecular Cell Biology (by Lodish et al, 5e) p.127 - Figure 4.17 The three roles of RNA in protein synthesis

Translation mechanism

in Eukaryotes

Molecular Cell Biology (by Lodish et al, 5e) p.113

Figure 4.1 Overview of four basic molecular genetic processes

Summary

Protein synthesis = Translation

Specificity of translation is determined by

- coding sequence (means that mRNA codon) - anticodon of transfer RNA

Elongation mechanism in translation

Translation mechanism in Eukaryotes