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Title: Modeling of the Passive Permeation of Mercury and Methylmercury Complexes Through a Bacterial Cytoplasmic Membrane

Abstract

Cellular uptake and export are important steps in the biotransformation of mercury (Hg) by microorganisms. However, the mechanisms of transport across biological membranes remain unclear. Membrane-bound transporters are known to be relevant, but passive permeation may also be involved. Inorganic Hg II and methylmercury ([CH 3Hg II] +) are commonly complexed with thiolate ligands. Here, we have performed extensive molecular dynamics simulations of the passive permeation of Hg II and [CH 3Hg II] + complexes with thiolate ligands through a model bacterial cytoplasmic membrane. Here, we find that the differences in free energy between the individual complexes in bulk water and at their most favorable position within the membrane are ~2 kcal mol -1. We provide a detailed description of the molecular interactions that drive the membrane crossing process. Favorable interactions with carbonyl and tail groups of phospholipids stabilize Hg-containing solutes in the tail–head interface region of the membrane. The calculated permeability coefficients for the neutral compounds CH3S–HgII–SCH3 and CH3HgII–SCH3 are on the order of 10 -5 cm s -1. Finally, we conclude that small, nonionized Hg-containing species can permeate readily through cytoplasmic membranes.

Authors:
ORCiD logo [1]; ORCiD logo [2];  [1];  [2];  [2]; ORCiD logo [1]
  1. Univ. of Tennessee, Knoxville, TN (United States). Graduate School of Genome Science and Technology; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Molecular Biophysics, Biosciences Division
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Molecular Biophysics, Biosciences Division; Univ. of Tennessee, Knoxville, TN (United States). Dept. of Biochemistry and Cellular and Molecular Biology
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1394306
DOE Contract Number:  
AC05-00OR22725; AC02-05CH11231; R25GM086761
Resource Type:
Journal Article
Journal Name:
Environmental Science and Technology
Additional Journal Information:
Journal Volume: 51; Journal Issue: 18; Journal ID: ISSN 0013-936X
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES

Citation Formats

Zhou, Jing, Smith, Micholas Dean, Cooper, Sarah J., Cheng, Xiaolin, Smith, Jeremy C., and Parks, Jerry M. Modeling of the Passive Permeation of Mercury and Methylmercury Complexes Through a Bacterial Cytoplasmic Membrane. United States: N. p., 2017. Web. doi:10.1021/acs.est.7b02204.
Zhou, Jing, Smith, Micholas Dean, Cooper, Sarah J., Cheng, Xiaolin, Smith, Jeremy C., & Parks, Jerry M. Modeling of the Passive Permeation of Mercury and Methylmercury Complexes Through a Bacterial Cytoplasmic Membrane. United States. doi:10.1021/acs.est.7b02204.
Zhou, Jing, Smith, Micholas Dean, Cooper, Sarah J., Cheng, Xiaolin, Smith, Jeremy C., and Parks, Jerry M. Mon . "Modeling of the Passive Permeation of Mercury and Methylmercury Complexes Through a Bacterial Cytoplasmic Membrane". United States. doi:10.1021/acs.est.7b02204.
@article{osti_1394306,
title = {Modeling of the Passive Permeation of Mercury and Methylmercury Complexes Through a Bacterial Cytoplasmic Membrane},
author = {Zhou, Jing and Smith, Micholas Dean and Cooper, Sarah J. and Cheng, Xiaolin and Smith, Jeremy C. and Parks, Jerry M.},
abstractNote = {Cellular uptake and export are important steps in the biotransformation of mercury (Hg) by microorganisms. However, the mechanisms of transport across biological membranes remain unclear. Membrane-bound transporters are known to be relevant, but passive permeation may also be involved. Inorganic HgII and methylmercury ([CH3HgII]+) are commonly complexed with thiolate ligands. Here, we have performed extensive molecular dynamics simulations of the passive permeation of HgII and [CH3HgII]+ complexes with thiolate ligands through a model bacterial cytoplasmic membrane. Here, we find that the differences in free energy between the individual complexes in bulk water and at their most favorable position within the membrane are ~2 kcal mol-1. We provide a detailed description of the molecular interactions that drive the membrane crossing process. Favorable interactions with carbonyl and tail groups of phospholipids stabilize Hg-containing solutes in the tail–head interface region of the membrane. The calculated permeability coefficients for the neutral compounds CH3S–HgII–SCH3 and CH3HgII–SCH3 are on the order of 10-5 cm s-1. Finally, we conclude that small, nonionized Hg-containing species can permeate readily through cytoplasmic membranes.},
doi = {10.1021/acs.est.7b02204},
journal = {Environmental Science and Technology},
issn = {0013-936X},
number = 18,
volume = 51,
place = {United States},
year = {2017},
month = {8}
}