Open AccessPermeation of tetracyclines through membranes of liposomes and Escherichia coli
Author(s) -
Sigler Albrecht,
Schubert Peter,
Hillen Wolfgang,
Niederweis Michael
Publication year - 2000
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1327.2000.01026.x
Subject(s) - tetr , permeation , membrane , escherichia coli , liposome , chemistry , tetracycline , diffusion , efflux , chromatography , synthetic membrane , biophysics , nuclear chemistry , biochemistry , antibiotics , biology , repressor , physics , thermodynamics , transcription factor , gene
Uptake of tetracycline (tc), 2‐tetracyclinonitrile (CN‐tc), and 9‐( N,N ‐dimethylglycylamido)‐6‐demethyl‐6‐deoxytetracycline (DMG‐DMDOT) by liposomes containing Tet repressor (TetR) and by Escherichia coli cells overexpressing TetR was examined. TetR specifically binds to tetracyclines, enhances their fluorescence and thereby allows selective detection of tetracyclines that have crossed the membranes. Analysis of the diffusion of tc and DMG‐DMDOT into liposomes yielded permeation coefficients of (2.4 ± 0.6) × 10 −9 cm·s −1 and (3.3 ± 0.8) × 10 −9 cm·s −1 , respectively. Similar coefficients were obtained for uptake of these tetracyclines by E. coli , indicating that diffusion through the cytoplasmic membrane is the rate‐limiting step. The permeation coefficients translate into half‐equilibration times of approximately 35 ± 15 min and explain how efflux pumps can mediate resistance against tetracyclines. Furthermore, diffusion of CN‐tc into liposomes was at least 400‐fold slower than that of tc, indicating that the carboxamide group at position C2 is required for efficient permeation of tc through lipid membranes and thereby explaining the lack of antibiotic activity of CN‐tc.