Mechanism of Action
Tetracyclines bind to the 30S subunit of microbial ribosomes. They inhibit protein synthesis by blocking the attachment of charged aminoacyl-tRNA to the A site on the ribosome. Thus, they prevent introduction of new amino acids to the nascent peptide chain. The action is usually inhibitory and reversible upon withdrawal of the drug. Resistance to the tetracyclines results from changes in permeability of the microbial cell envelope. In susceptible cells, the drug is concentrated from the environment and does not readily leave the cells. In resistant cells, the drug is not actively transported into the cells or leaves it so rapidly, inhibitory concentrations are not maintained. This is often plasmid-controlled. Mammalian cells are not vulnerable to the effect of tetracyclines, as these contain no 30S ribosomal subunits, so do not accumulate the drug.
Read more about this topic: Tetracycline
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