Tetracycline Mechanism: Inhibiting Protein Synthesis
Tetracycline is an antibiotic medication used to treat various bacterial infections. Its effectiveness comes from selectively inhibiting bacterial protein synthesis.
Mode of Action
Tetracycline targets the bacterial ribosome, specifically the 30S ribosomal subunit. Its primary mechanism is:
- Inhibiting the binding of amino-acyl tRNA to the A (aminoacyl) site of the ribosome.
This prevents the correct amino acid, carried by the tRNA, from entering the ribosome to be added to the growing polypeptide chain. Consequently, protein synthesis is halted.
Analysis of Options
- Option 1: interaction between tRNA and mRNA - This involves codon-anticodon pairing, which Tetracycline does not directly inhibit.
- Option 2: translocation of mRNA through ribosome - This step, moving the ribosome along the mRNA, is inhibited by other antibiotics (e.g., macrolides), not Tetracycline.
- Option 3: peptidyl transferase activity - This activity forms peptide bonds and is inhibited by drugs like chloramphenicol.
- Option 4: binding of amino-acyl tRNA to ribosome - This is the precise step inhibited by Tetracycline, as explained above.
Therefore, Tetracycline's action is specifically preventing the delivery of new amino acids to the ribosome via tRNA.
Important Questions from Antibiotics and Antimicrobial Resistance
- Which one of the following antibiotics blocks protein chain elongation by preventing the action of peptidyl transferase ?
Match the antibiotics in Group I with their modes of action in Group II.
Group I Group II P) Chloramphenicol 1) Inhibits protein synthesis by acting on 30S ribosomal subunit Q) Rifampicin 2) Interferes with DNA replication by inhibiting DNA gyrase R) Tetracycline 3) Inhibits protein synthesis by acting on 50S ribosomal subunit S) Quinolone 4) Interferes with RNA polymerase activity 5) Inhibits $\beta$-lactamase activity - Which of the following statement(s) is(are) TRUE about fluoroquinolone drugs?
- A list of pathogens (Group I) and a list of anti-microbial agents (Group II) used to treat their infections are given below. Match the pathogens with the corresponding anti-microbial agents.
Group I Group II [P] Influenza A virus 1. Isoniazid [Q] Fungus 2. Amantadine [R] Plasmodium 3. Fluconazole [S] Mycobacterium 4. Artemisinin 5. Iodoquinol A bacterial culture (200 µl containing $1.8 \times 10^9$ cells) was treated with an antibiotic Z (50 µg per ml) for 4 h at 37°C. After this treatment, the culture was divided into two equal aliquots.
Set A: 100 µl was plated on Luria agar.
Set B: 100 µl was centrifuged, the cell pellet washed and plated on Luria agar.
After incubating these two plates for 24 h at 37°C, Set A plate showed no colonies, whereas the Set B plate showed $0.9 \times 10^9$ cells. This experiment showed that the antibiotic Z is
