MECHANISM OF ACTION OF A 16-MEMBERED MACROLIDE: CHARACTERISTICS OF DIHYDROROSARAMICIN BINDING TO ESCHERICHIA COLI RIBOSOME AND THE EFFECTS OF SOME COMPETITORS

The macrolide [13H]dihydrorosaramicin binds specifically to 50S and 70S bacterial ribosomal particles. We have studied the influence of salts, pH and additives on the interaction and found that the optimum requirement for salts was 10 mM tris-HCl (pH 7.6), 6 mM MgCl2, 60 mM NH4Cl, and the β-mercaptoethanol which reacts on rosaramicin and its dihydro derivative cannot be used. The parameters of the binding were not dependent on the technique used, i.e. equilibrium dialysis, ethanol precipitation or two-phase partitioning. In our search for effectors of this binding, we have found that it is inhibited by other macrolides, little effected by tobramycin and chloramphenicol and enhanced by puromycin.