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Structure and mechanism of the chalcogen-detoxifying protein TehB fromEscherichia coli
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Choudhury, Hassanul G., Cameron, Alexander, Iwata, So and Beis, Konstantinos (2011) Structure and mechanism of the chalcogen-detoxifying protein TehB fromEscherichia coli. Biochemical Journal, Vol. 435 (No. 1). pp. 85-91. doi:10.1042/BJ20102014 ISSN 0264-6021.
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Official URL: http://dx.doi.org/10.1042/BJ20102014
Abstract
The oxyanion derivatives of the chalcogens tellurium and selenium are toxic to living organisms even at very low levels. Bacteria have developed mechanisms to overcome their toxicity by methylating them. The structure of TehB from Escherichia coli has been determined in the presence of the cofactor analogues SAH (S-adenosylhomocysteine) and sinefungin (a non-hydrolysable form of S-adenosyl-L-methionine) at 1.48 Å (1 Å=0.1 nm) and 1.9 Å respectively. Interestingly, our kinetic data show that TehB does not discriminate between selenium or tellurite oxyanions, making it a very powerful detoxifying protein. Analysis of the active site has identified three conserved residues that are capable of binding and orientating the metals for nucleophilic attack: His176, Arg177 and Arg184. Mutagenesis studies revealed that the H176A and R184A mutants retained most of their activity, whereas the R177A mutant had 65% of its activity abolished. Based on the structure and kinetic data we propose an SN2 nucleophilic attack reaction mechanism. These data provide the first molecular understanding of the detoxification of chalcogens by bacteria.
Item Type: | Journal Article | ||||
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Divisions: | Faculty of Science, Engineering and Medicine > Science > Life Sciences (2010- ) | ||||
Journal or Publication Title: | Biochemical Journal | ||||
Publisher: | Biochemical Society | ||||
ISSN: | 0264-6021 | ||||
Official Date: | 2011 | ||||
Dates: |
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Volume: | Vol. 435 | ||||
Number: | No. 1 | ||||
Page Range: | pp. 85-91 | ||||
DOI: | 10.1042/BJ20102014 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Access rights to Published version: | Restricted or Subscription Access |
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