Evernimicin binds exclusively to the 50S ribosomal subunit and inhibits translation in cell-free systems derived from both gram-positive and gram-negative bacteria

Evernimicin (SCH 27899) is a new antibiotic with activity against a wide sp ectrum of gram-positive bacteria and activity against some gram-negative ba cteria. Previous metabolic labeling studies indicated that evernimicin spec ifically inhibited protein synthesis in Staphylococcus aureus. Using a susc eptible Escherichia coli strain, we demonstrated that evernimicin also inhi bited protein synthesis in E. coli. In cell-free translation assays with ex tracts from either E. coli or S. aureus, evernimicin had a 50% inhibitory c oncentration of approximately 125 nM. In contrast, cell-free systems derive d from wheat germ and rabbit reticulocytes were inhibited only by very high levels of evernimicin. Evernimicin did not promote transcript misreading, [C-14]evernimicin specifically bound to the 50S subunit from E. coli. Nonli near regression analysis of binding data generated with 70S ribosomes from E. coli and S. aureus and 50S subunits from E, coil returned dissociation c onstants of 84, 86, and 160 nM, respectively. In binding experiments, perfo rmed in the presence of excess quantities of a selection of antibiotics kno wn to bind to the 50S subunit, only the structurally similar drug avilamyci n blocked binding of [C-14]evernimicin to ribosomes.