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Journal of Bacteriology, November 2000, p. 6509-6513, Vol. 182, No. 22
Department of Medical Microbiology and
Immunology1 and Department of
Biochemistry,3 University of Alberta, Edmonton,
Alberta T6G 2H7, and Structural Biology Research Group,
Department of Biological Sciences, University of Calgary, Calgary,
Alberta T2N 1N4,2 Canada
Received 30 May 2000/Accepted 1 September 2000
The Escherichia coli chromosomal determinant for
tellurite resistance consists of two genes (tehA and
tehB) which, when expressed on a multicopy plasmid, confer
resistance to K2TeO3 at 128 µg/ml, compared
to the MIC of 2 µg/ml for the wild type. TehB is a cytoplasmic protein which possesses three conserved motifs (I, II, and III) found
in S-adenosyl-L-methionine (SAM)-dependent
non-nucleic acid methyltransferases. Replacement of the conserved
aspartate residue in motif I by asparagine or alanine, or of the
conserved phenylalanine in motif II by tyrosine or alanine, decreased
resistance to background levels. Our results are consistent with motifs
I and II in TehB being involved in SAM binding. Additionally,
conformational changes in TehB are observed upon binding of both
tellurite and SAM. The hydrodynamic radius of TehB measured by dynamic
light scattering showed a ~20% decrease upon binding of both
tellurite and SAM. These data suggest that TehB utilizes a
methyltransferase activity in the detoxification of tellurite.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Escherichia coli TehB Requires
S-Adenosylmethionine as a Cofactor To Mediate
Tellurite Resistance
*
Corresponding author. Mailing address: Department of
Biological Sciences, University of Calgary, 2500 University Dr. N.W., Calgary, Alberta T2N 1N4, Canada. Phone: (403) 220-4308. Fax: (403)
289-9311. E-mail: turnerr{at}ucalgary.ca.
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