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Direct Measurement of Mercury(II) Removal from Organomercurial Lyase (MerB) by Tryptophan Fluorescence: NmerA Domain of Coevolved γ-Proteobacterial Mercuric Ion Reductase (MerA) Is More Efficient Than MerA Catalytic Core or Glutathione,

Journal Article · · Biochemistry
DOI:https://doi.org/10.1021/bi100802k· OSTI ID:1038457
 [1];  [2];  [3];  [4]
  1. Department of Pharmaceutical Chemistry; University of California San Francisco
  2. Department of Pharmaceutical Chemistry
  3. Graduate Group in Biophysics
  4. Department of Pharmaceutical Chemistry; Graduate Group in Biophysics
+ Show Author Affiliations
Aerobic and facultative bacteria and archaea harboring mer loci exhibit resistance to the toxic effects of Hg(II) and organomercurials [RHg(I)]. In broad spectrum resistance, RHg(I) is converted to less toxic Hg(0) in the cytosol by the sequential action of organomercurial lyase (MerB: RHg(I) → RH + Hg(II)) and mercuric ion reductase (MerA: Hg(II) → Hg(0)) enzymes, requiring transfer of Hg(II) from MerB to MerA. Although previous studies with γ-proteobacterial versions of MerA and a nonphysiological Hg(II)-DTT-MerB complex qualitatively support a pathway for direct transfer between proteins, assessment of the relative efficiencies of Hg(II) transfer to the two different dicysteine motifs in γ-proteobacterial MerA and to competing cellular thiol is lacking. Here we show the intrinsic tryptophan fluorescence of γ-proteobacterial MerB is sensitive to Hg(II) binding and use this to probe the kinetics of Hg(II) removal from MerB by the N-terminal domain (NmerA) and catalytic core C-terminal cysteine pairs of its coevolved MerA and by glutathione (GSH), the major competing cellular thiol in γ-proteobacteria.
Research Organization:
Univ. of California, San Francisco, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
DOE Contract Number:
FG02-05ER64120
OSTI ID:
1038457
Report Number(s):
DOE/ER/64120-P1
Journal Information:
Biochemistry, Journal Name: Biochemistry Journal Issue: 37 Vol. 49; ISSN 0006-2960
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English

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