Protein biosynthesis (translation)
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Protein Biosynthesis (Translation) This presentation explains the reactions of protein biosynthesis (Translation) in simple diagrammatic format.
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Protein biosynthesis (translation)
- 2. Central Dogma RNA DNA Protein Transcription Translation Replication Reverse Transcription The flow of information in the cell starts at DNA, which re plicates to form more DNA. Information is then ‘transcribed” into RNA, and then it is “translated” into protein. The proteins do most of the work in the cell.
- 5. Translation The pathway of protein Biosynthesis is called translation Interpreting the information coded in the mRNA into proteins The nucleotides are read in triplets (set of three) called codons Each triplet code for a specific amino acid, & sometimes more than one codon exist for an amino acid mRNA are read by the translational machinery including ◦ ribosomes, ◦ tRNAs and ◦ rRNAs
- 6. Protein Synthesis protein synthesis in eukaryotes is similar to that in prokaryotes. However, eukaryotic protein synthesis involves more protein components & some steps are more intricate.
- 7. Basic Requirements for the Translation mRNA to be translated tRNAs Ribosomes Energy in the form of ATP and GTP Enzymes and specific factors
- 11. Ribosomes
- 12. Stages of Translation There are four major stages in protein synthesis, each requiring a number of co mponents. Elongation Initiation Activation of amino acids Termination
- 13. Activation of Amino Acid Activation of amino acid takes place in the cytosol. In activation of amino acid each of the 20 amino acids, is covalently attached to their respective tRNA, at the expense of ATP, by aminoacyl tRNA synthetase (AAS) enzyme. tRNA + Amino acid +ATP + AMP + PPi Aminoacyl tRNA U A C U A C
- 14. Initiation Initiation can be divided into four steps : Ribosomal dissociation STEP 1 Formation of 43S pre-initiation complex. STEP 2 Formation of 48S initiation complex STEP 3 Formation of 80S initiation complex STEP 4
- 16. 2 1A 3 GTP eIF1 1 2 GTP 43S Preinitiation complex Formation of 43S pre- initiation complex. eIF3 eIF1A40S 60S P Site A Site Inactive 80S ribosome 1A3 60S 40S
- 17. 1A 3 1 2 GTP 43S Preinitiation complex A U G5’ 3’ Cap ATP 4G 4A 4E 4F A U G5’ 3’ Cap 4F ATP ADP + Pi 4A 4B A U G5’ 3’ Cap 4F 4A 4B 4A 4B 1A 3 1 2 GTP 43S Initiation complex A U G5’ 3’ Cap 4F 48S Initiation complex 1A 3 1 2 GTP A U G5’ 3’ Cap ATP ADP + Pi mRNA Formation of 48S initiation complex
- 18. 48S Preinitiation complex 1A 3 1 2 GTP A U G5’ 3’ Cap 1A 31 2 GDP A U G5’ 3’ Cap Formation of 80S initiation complex A U G5’ 3’ Cap P Site A Site GTP GDP + Pi 60S 80S Initiation complex eIF5
- 19. Elongation • Elongation can be divided into three steps… Binding of next aminoacyl tRNA to the A site of ribosome STEP 1 Formation of peptide bond STEP 2 Translocation STEP 3
- 20. P Site A Site Peptidyl transferase 80S Initiation complex AUG GUU CCA5’ 3’ Cap EF1α GTP EF1α GDP + Pi P Site A Site AUG GUU CCA5’ 3’ Cap P Site A Site AUG GUU CCA5’ 3’ Cap EF2 GTP EF2 GDP + Pi P Site A Site AUG GUU CCA5’ 3’ Cap Binding of next aminoacyl tRN A to the A site of ribosome Formation of peptide bond Translocation Binding of next aminoacyl tRNA to the A site of ribo some STEP 1 Formationof peptidebond STEP 2 Translocation STEP 3 Repeated
- 21. P Site A Site 5’ 3’ Cap O O = OC CH R NH2 = OC CH R NH = OC CH R NH … P Site A Site 5’ 3’ Cap OH O = OC CH R NH = OC CH R NH =OC CH R NH … Peptidyl-tRNA Aminoacyl-tRNA Formation of peptide bond EF2
- 22. P Site A Site G U U C C A G A U C A C5’ 3’ Cap A U G
- 23. P Site A Site Termination P Site A Site U A G5’ 3’ Cap 80S Initiation complex RF-1 U A G5’ 3’ Cap RF-1 U A G5’ 3’ Cap
- 24. Post-translational Modification • In order to achieve native biologically active form of the polypeptide, it must undergo folding into its proper 3 D conformation. • This is achieved by group of specialized proteins The chap erones ensure the folding of protein into its native for m. • Before or, after folding, the polypeptide may undergo processing by enzymatic action. • Collectively these alterations are known as post translati onal modifications.
- 25. Post-translational Modification • Some of post-translational modifications are… – Amino Terminal Modifications – Loss of Signal Sequence – Covalent Modification of Proteins • Glycosylation • Phosphorylation • Carboxylation (eg. glutamic acid residues of prothrombin) • Hydroxylation (eg. collagen) • Methylation (eg. muscle proteins and cytochrome C) • Addition of prosthetic group (eg. heme gr of cytochrome) – Proteolytic Processing
- 26. Inhibitors Of Protein Synthesis • A number of commonly used variety of antibiotics, act by inhi biting selectively the process of prokaryotic protein b iosynthesis. • Binds to the 30S subunit of prokaryotes at the A site • Inhibits chain elongation Streptomycin • Binds to the 30S subunit • Inhibits binding of aminoacyl tRNA to mRNA Tetracycline • Binds to the 50S ribosomal subunit • Blocks the peptidyl transferase reaction Chloramphenicol • Binds to the 50S ribosomal subunit • Inhibits the translocation reaction Erythromycin
- 27. Protein Biosynth esis (Translation)Ashok Katta Thank yo u Ashok Katta Dept. of Biochemistry, Dhanalakshmi Srinivasan Medical College, Perambalur Contact no. - +917418831766 E mail - For more presentation visit -
Editor's Notes
- Central Dogma 是生物界中心的基本運作法則，而其主角就是核酸，包括 DNA 及 RNA。 Central dogma 說明了遺傳信息由 DNA 流到 RNA 再到蛋白質的過程； 而其之所以能夠運作，與核酸的分子構造，有極大的關係；分子生物學就是以分子的層次，探討整個 Central Dogma 的作用機制。