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Antimicrobial Agents and Chemotherapy, Feb 1997, 440-444, Vol 41, No. 2
RJ Turner, DE Taylor and JH Weiner
The genes tehAB located at 32.3 min on the Escherichia coli chromosome were
initially identified by their ability to mediate resistance to potassium
tellurite (128 micrograms of K2TeO3 per ml) when overexpressed with a
high-copy-number plasmid. The genes encode an integral membrane protein
(TehA) of 36 kDa with 10 putative transmembrane segments and a second
protein (TehB) of 23 kDa. Overexpression of TehAB results in
hypersensitivity to dequalinium CI and methyl viologen (paraquat).
Expression of TehA alone gives similar hypersensitivity. Overexpression of
TehA gave resistance to tetraphenylarsonium CI, ethidium bromide, crystal
violet and proflavin. The efflux of ethidium, measured by fluorescence
quenching, revealed that TehA transported ethidium at twice the control
rate and 10% of the rate of the highly resistant efflux transporter Emr
Eco. Addition of tellurite had no effect on ethidium transport. In addition
to the ethidium transport assay, a proflavin fluorescence assay which was
approximately 200-fold more sensitive was also used. TehA was also found to
have proflavin efflux activity. The addition of TeO32- to the proflavin
transport assay on TehA caused a 20% increase in transport rate. Both
ethidium and proflavin transport were found to be energy dependent.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
Expression of Escherichia coli TehA gives resistance to antiseptics and disinfectants similar to that conferred by multidrug resistance efflux pumps
Department of Biochemistry, University of Alberta, Edmonton, Canada.
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