The Journal of Biochemistry
Online ISSN : 1756-2651
Print ISSN : 0021-924X
Evidence for Chloramphenicol/H+ Antiport in Cmr (MdfA) System of Escherichia coli and Properties of the Antiporter
Tomoyuki MineYuji MoritaAtsuko KataokaTohru MizushimaTomofusa Tsuchiya
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JOURNAL FREE ACCESS

1998 Volume 124 Issue 1 Pages 187-193

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Abstract

We detected chloramphenicol/H+ antiport activity in membrane vesicles of Escherichia coli and cloned a gene for the antiporter from chromosomal DNA of E. coli. Introduction of the gene into E. coli cells conferred resistance to chloramphenicol and ethidium. A slight increase in resistance to acridine orange was also observed. Elevated chloramphenicol efflux and ethidium efflux were observed in cells harboring a plasmid carrying the gene. Addition of chloramphenicol to the assay mixture reduced the efflux of ethidium. Elevated chloramphenicol/H+ antiport activity was observed in membrane vesicles prepared from cells harboring the plasmid. The pH optimum for the activity was 6.5. We sequenced the gene and deduced the amino acid sequence of its product. A sequence homology search revealed that it was same as that of Cmr (or MdfA). Thus, it became clear that Cmr (MdfA) is the chloramphenicol(and ethidium)/H+ antiporter.

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© The Japanese Biochemical Society
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