Erythromycin acts by interfering with:
Correct Answer: Translocation of 50S ribosome
Description: ERYTHROMYCIN It was isolated from Streptomyces erythreus in 1952. Since then it has been widely employed, mainly as alternative to penicillin. Water solubility of erythromycin is limited, and the solution remains stable only when kept in cold. Mechanism of action Erythromycin is bacteriostatic at low but cidal (for ceain bacteria) at high concentrations. Cidal action depends on the organism concerned and its rate of multiplication. Sensitive gram-positive bacteria accumulate erythromycin intracellularly by active transpo which is responsible for their high susceptibility to this antibiotic. It is several fold more active in alkaline medium, because the nonionized (penetrable) form of the drug is oured at higher pH. Erythromycin acts by inhibiting bacterial protein synthesis. It combines with 50S ribosomes subunits and interferes with 'translocation' . After peptide bond formation between the newly attached amino acid and the nacent peptide chain at the acceptor (A) site the elongated peptide is translocated back to the peptidyl (P) site, making the A site available for next aminoacyl tRNA attachment. This is prevented by erythromycin and the ribosome fails to move along the mRNA to expose the next codon. As an indirect consequence, peptide chain may be prematurely terminated: synthesis of larger proteins is especifically suppressed. Essentials of medical pharmacology K D Tripathi Sixth edition Pg no 727
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