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Journal of Bacteriology, February 2006, p. 1191-1195, Vol. 188, No. 3
0021-9193/06/$08.00+0     doi:10.1128/JB.188.3.1191-1195.2006

Mammalian Steroid Hormones Are Substrates for the Major RND- and MFS-Type Tripartite Multidrug Efflux Pumps of Escherichia coli

Christopher A. Elkins^* and Lisa B. Mullis

Division of Microbiology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, Arkansas 72079-9502

Received 30 September 2005/ Accepted 4 November 2005

A steroid-hormone-dependent growth suppression was observed in Escherichia coli efflux-deficient backgrounds containing mutations in the major RND- and MFS-type tripartite multidrug efflux systems, AcrAB-TolC and EmrAB-TolC, respectively. In addition to their previously known natural steroid spectrum, which includes bile acids, both systems were shown to transport the hormones estradiol and progesterone, whereas hydrocortisone served as a substrate of only AcrAB-TolC. Furthermore, at least two other RND-type pumps, YhiV and AcrD, were capable of transporting such hormones when overexpressed on plasmid vectors (with some demonstrable specificity observed with AcrD). When this activity was examined in a wild-type background, cell-associated estradiol levels remained largely unaffected by competition with exogenous bile acids and hydrocortisone, in contrast to progesterone, which produced a significant modulation in estradiol uptake.

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* Corresponding author. Mailing address: Division of Microbiology, National Center for Toxicological Research, 3900 NCTR Drive, Jefferson, AR 72079-9502. Phone: (870) 543-7547. Fax: (870) 543-7307. E-mail: chris.elkins{at}fda.hhs.gov.

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Journal of Bacteriology, February 2006, p. 1191-1195, Vol. 188, No. 3
0021-9193/06/$08.00+0     doi:10.1128/JB.188.3.1191-1195.2006

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