Transport of aminoglycosides in Escherichia coli.

Uptake of nine aminoglycosides was studied in E. coli K12 and mutants being defective in the outer membrane proteins OmpF and OmpC or in ATPase (uncA). OmpF/OmpC as well as uncA mutants did not take up the aminoglycosides; transport in wild type cells was cAMP dependent. The specific binding of phages using the OmpF and OmpC proteins as receptors was strongly reduced by the aminoglycosides or by other polycationic peptides. Thus it may be assumed that the initial step of aminoglycoside transport is their electrostatic binding to the anionic porins, especially to the ompF porin, followed by a facilitated permeation through the outer membrane. As the synthesis of this porin is under cAMP control, aminoglycoside transport is cAMP dependent as well. The fact that the uncA mutant did not take up the aminoglycosides to any appreciable extent indicates that the cytoplasmic membrane is involved in aminoglycoside transport too.