title: Inhibition of polypeptide synthesis in cell-free systems by virginiamycin S and erythromycin. Evidence for a common mode of action of type B synergimycins and 14-membered macrolides.
abstract: Macrolides, lincosamides and type B synergimycins are powerful inhibitors of protein synthesis in vivo, but many of them were found to be inactive in vitro. In the present work, we confirm that virginiamycin S (a type B synergimycin) and erythromycin (a 14-membered macrolide) have no effect on poly(U)-directed poly(Phe) synthesis. However, the amino-acid polymerization reactions directed by poly(U,G), poly(U,C), poly(A,G) and poly(A,C) were increasingly inhibited (20-50%) by both antibiotics. The action of these inhibitors proved to be template-dependent and favored by the incorporation of proline and of basic amino acids into peptides. Under these conditions, virginiamycin S and erythromycin markedly stimulated a release of peptidyl-tRNA from the ribosomes. In the poly(A,C) model system, these antibiotics produced a 50% inhibition of amino-acid incorporation into total peptides, a 70% release of ribosome-bound peptidyl-tRNA, and a 95% repression of the synthesis of long peptide chains. The production of equivalent effects at saturating concentrations of these antibiotics in the four model systems examined is suggestive of a similarity in their mode of action. Our results indicate that 14-membered macrolides and type B synergimycins can act on ribosomes during the whole elongation process. The functional block produced by both antibiotics is usually reversible, but may result in a premature release of peptidyl-tRNA when the stability of ribosomal complexes is lowered by the incorporation of basic amino acids.
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000096:biosynthesis*; D004917:Erythromycin / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D014176:Protein Biosynthesis / Q000187:drug effects; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014769:Virginiamycin / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D014769:Virginiamycin; D004917:Erythromycin