Practice question

Erythromycin macrolide contains 14-membered lactone ring with L-desosamine sugar binding nascent peptide exit tunnel of 50S subunit near peptidyl transferase center contacting 23S rRNA A2058, A2059. Binding does not prevent peptide bond formation initially but blocks nascent chain progression through tunnel after six to eight residues, inhibiting translocation where deacylated tRNA moves P to E and peptidyl-tRNA A to P via EF-G. Abortive peptidyl-tRNA drop-off occurs terminating translation prematurely. Resistance via erm methyltransferase methylating A2058 preventing interaction. Bacteriostatic activity against Gram-positive cocci, atypical bacteria, mycoplasma relies on elongation-translocation blockade explaining post-antibiotic effect and protein synthesis inhibition mechanism clinically relevant.