No Nucleus Advantage
- Because bacteria lack a nuclear membrane, transcription and translation happen at the same time
- Forms a polyribosomal complex for faster protein production
3 stages of prokaryotic protein synthesis
- Initiation
- Elongation
- Termination
Bacterial ribosomal subunits
30S and 50S
Eukaryotic ribosomal subunits
40S and 60S
Initiation of Translation in Bacteria
- Bacterial translation begins with the initiator tRNA N-formylmethionyl-tRNAᶠᴹᵉᵗ
- Starts protein synthesis and is later removed from the mature protein
Bacterial translation initiation - Step 1
Initiation factors 1/2/3, GTP, fMet-tRNAᶠᴹᵉᵗ, and 30S subunit assemble with the mRNA
Bacterial translation initiation - Step 2
- 50S subunit joins the complex
- IF2 hydrolyzes GTP and releases IF1 and IF3
- Results in 70S initiation complex
Bacterial translation initiation - Step 3
Complex is ready for elongation
Elongation in Bacteria
- During elongation, tRNAs bring amino acids to the ribosome according to the mRNA sequence
- EF-Tu delivers charged tRNAs
- EF-G moves tRNA and mRNA through the ribosome
Translocation
Moves the mRNA–tRNA complex along the ribosome, shifting the next codon into the A-site for continued protein elongation
Peptide-Bond Formation
A peptide bond forms by a dehydration reaction linking the carboxyl group of one amino acid to the amino group of another
Nascent Chain Elongation
Is the complex of a ribosome attached to the growing polypeptide chain it is synthesizing
Termination
When a stop codon (UAG, UAA, or UGA) enters the A-site, release factors free the completed polypeptide and trigger ribosome disassembly
Recycling
After termination, the ribosomal subunits and tRNA are recycled to form new initiation complexes for another round of translation
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Module 1: Section 124
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Module 1: Section 236
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Module 2: Section 1A26
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Module 2: Section 1B54
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Module 2: Section 1C8
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Module 2: Section 1D7
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Module 2: Section 2A16
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Module 2: Section 2B6
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Module 2: Section 2C5
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Module 2: Section 2D12
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Module 3: Section 1A15
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Module 3: Section 1B19
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Module 3: Section 1C16
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Module 3: Section 2A18
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Module 3: Section 2B22
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Module 3: Section 2C31
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Module 3: Section 2D23
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Module 3: Section 2E14
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Module 4: Section 1A24
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Module 4: Section 1B24
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Module 4: Section 2A15
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Module 4: Section 2B14
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Module 4: Section 3A34
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Module 4: Section 3B31
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Module 4: Section 3C21
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Module 5: Section 1A15
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Module 5: Section 1B9
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Module 5: Section 1C14
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Module 5: Section 2A30
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Module 5: Section 2B13
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Module 5: Section 2C32
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Module 6: Section 1A15
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Module 6: Section 1B24
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Module 6: Section 1C14
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Module 6: Section 2A14
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Module 6: Section 2B32
