Escherichia coliTehB RequiresS-Adenosylmethionine as a Cofactor To Mediate Tellurite Resistance
- 15 November 2000
- journal article
- research article
- Published by American Society for Microbiology in Journal of Bacteriology
- Vol. 182 (22) , 6509-6513
- https://doi.org/10.1128/jb.182.22.6509-6513.2000
Abstract
TheEscherichia colichromosomal determinant for tellurite resistance consists of two genes (tehAandtehB) which, when expressed on a multicopy plasmid, confer resistance to K2TeO3at 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 inS-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.Keywords
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