Mechanism of action of aminoglycoside antibiotics. Binding studies of tobramycin and its 6'-N-acetyl derivative to the bacterial ribosome and its subunits.
6'-N-[14C]Acetyl-tobramycin and [3H]tobramycin were synthesized and their binding to Escherichia coli ribosomes and ribosomal subunits studied using equilibrium dialysis. THE 70-S ribosome, as well as its 50-S and 30-S subunits, bound tightly to 6'-N-acetyl-tobramycin. The binding of [3H]tobramycin to ribosomes was quite different. The 70-S ribosome was observed to possess several classes of binding sites; of these, one was determined to be of higher affinity and lower capacity, the 6'-N-[14C]acetyl-tobramycin site. The isotopic dilution method was used to define the specificity of the interaction. The selective binding of 6'-N-[14C]acetyl-tobramycin was highly reversible by tobramycin, kanamycins A, B, C and neomycin, but not by streptomycin or erythromycin. Gentamicin C1a was a poor inhibitor. This suggested that either the kanosamin or garosamin rings might be determinant in the binding of these molecules, as well as the 6'-amino group.
D000900:Anti-Bacterial Agents / Q000378:metabolism* / Q000494:pharmacology; D001665:Binding Sites; D001667:Binding, Competitive; D004926:Escherichia coli / Q000378:metabolism; D007700:Kinetics; D012270:Ribosomes / Q000378:metabolism*; D013379:Substrate Specificity; D014031:Tobramycin / Q000031:analogs & derivatives / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D014031:Tobramycin