BINDING OF ERYTHROMYCIN TO ESCHERICHIA COLI RIBOSOMES

Abstract

This paper concerns a precise study on the nature of the binding of erythromycin to Escherichia coli (Q13) ribosomes. (1) An equimolar amount of erythromycin bound to 50S ribosomal subunits at extremely low concentrations and this binding was not affected by the addition of 30S ribosomal subunits. (2) The binding of erythromycin to ribosomes was not significantly influenced by decreasing the Mg⁺⁺ concentration to 10^-4M, although it was
dependent upon the concentration of K⁺ or NH₄⁺ as previously reported. Other components required for protein synthesis showed little effect on the binding. (3) Washing the ribosomes with NH₄Cl did not influence their erythromycin-binding capacity or their dependence on K⁺ or NH₄⁺. The addition of Li⁺ caused a remarkable inhibition of the antibiotic binding and this inhibition was reversed by the concomitant addition of NH₄⁺. (4) The erythromycin-binding ability of ribosomes from Bacillus subtilis, gram-positive bacteria, was roughly the same as that of those from gram-negative E. coli. In contrast to bacterial ribosomes, rabbit reticulocyte ribosomes bound erythromycin hardly at all.