Bacterial uptake of habekacin, a novel aminoglycoside antibiotic.

Abstract

Cellular uptake of habekacin, 1-N-(4-amino-2-hydroxybutyryl)dibekacin, was studied by incubating exponentially growing culture of Escherichia coli Q13 and its kanamycin-resistant mutants with [3H]habekacin. Kanamycin-resistant mutants, in which the resistance is due to alteration of ribosomes, were cross-resistant to habekacin, and showed a lower uptake of [3H]habekacin than the parental cells, suggesting that binding to ribosomes accelerates cellular uptake of habekacin. Cellular accumulation of [3H]habekacin by wild type cells was markedly inhibited by low temperature and by 2,4-dinitrophenol, suggesting that uptake of habekacin involves energy-dependent transport. The uptake of [3H]habekacin was reduced by various aminoglycoside antibiotics, suggesting common transport systems and/or common internal binding sites on the ribosome. Intracellular accumulation of [3H]dibekacin was reduced by habekacin, suggesting that both antibiotics possess a common transport system and/or common binding sites on the ribosome. Dibekacin was a better competitor than amikacin, suggesting that the dibekacin moiety of habekacin molecule, but not the 4-amino-2-hydroxybutyryl moiety, participates in the transport and/or binding to the ribosome. Binding of [3H]habekacin to E. coli ribosomes was reversed by various aminoglycosides and the degree of inhibition paralleled the one of cellular uptake, suggesting that competition by aminoglycosides for the habekacin uptake occurs at the ribosomal level.