Uptake of tetracycline by membrane preparations from Escherichia coli

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Abstract
1. A membrane fraction from Escherichia coli has been prepared essentially free from ribosomes by treatment of the membranes with Triton X-100 at 0°C followed by differential centrifugation. 2. The ribosome-free membrane vesicles absorbed tetracycline by a reversible temperature-dependent process with an apparent Km of 0.029mm at pH7.5 and 37°C. 3. The absorption process was negligible below 25°C and had an optimum at 40°C; a pH optimum at 7.5 was observed. 4. The absorption of tetracycline was strongly inhibited by EDTA and ATP; ADP inhibited less strongly and AMP had no effect. 5. There was no significant difference in the rates or extent of uptake of tetracycline by membranes prepared from tetracycline-sensitive and tetracycline-resistant, R-factor-bearing E. coli.