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The following points highlight the six antibiotics used in inhibitors of protein synthesis. The antibiotics are: 1. Chloramphenicol 2. Puromycin 3. Streptomycin 4. Actinomycin 5. Tetracyclins and 6. Cycloheximide.
Antibiotic # 1. Chloramphenicol (Chloromycetin):
It inhibits the protein synthesis by interfering with the transfer of amino acids by s-RNA to ribosomes (70 S only).
Antibiotic # 2. Puromycin:
This antibiotic inhibits the protein synthesis specifically and reversibly. It prevents the elongation of polypeptide chain because it has a free amino group which forms a peptide linkage with the terminal carboxylic group of the growing polypeptide chain.
Antibiotic # 3. Streptomycin:
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This antibiotic does not inhibit protein synthesis per se (as such) but seems to alter the ribosomes so that translation mechanism is disturbed, yielding inactive protein. This antibiotic was discovered by S.A. Waksman, Nobel Laureate of 1952 in Physiology or Medicine category.
Antibiotic # 4. Actinomycin:
This antibiotic inhibits the protein synthesis by inhibiting the DNA-directed synthesis of m-RNA, i.e., the inhibition occurs at transcription level.
Antibiotic # 5. Tetracyclins:
These inhibit protein synthesis in bacteria by blocking the ‘A’ site on the ribosome, so that binding of amino-acyl-tRNAs is inhibited.
Antibiotic # 6. Cycloheximide:
It inhibits protein synthesis by blocking the peptidyl transferase of eukaryotic ribosomes (80 S only). Besides these, some toxins such as Diphtheria toxin and ricin are potent inhibitors of protein synthesis. Diphtheria toxin inactivates eukaryotic elongation factor eEF2 while ricin (from castor bean) inactivates 60 S subunit of eukaryotic ribosomes.
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(Venkatraman, Ramakrishnan, Thomas A. Steitz and Ada E Yonath jointly shared Nobel Prize of 2009 in Chemistry for their pioneer and collaborative work on structure and function of ribosomes which are crucial to life and are also a major target for new antibiotics.
By using X-Ray Crystallography, these scientists mapped the position of each and every one of the hundreds of thousands of atoms that make up the ribosome and generated three dimensional models that show how different antibiotics bind to ribosomes. Their work will immensely help produce antibiotics that are not resistant to bacteria as it has become resistant to many of the drugs now on the market.)
