Modeling of the Passive Permeation of Mercury and Methylmercury Complexes Through a Bacterial Cytoplasmic Membrane
[1];
[2];
[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
- 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
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.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Biological and Environmental Research (BER)
- DOE Contract Number:
- AC05-00OR22725; AC02-05CH11231; R25GM086761
- OSTI ID:
- 1394306
- Journal Information:
- Environmental Science and Technology, Vol. 51, Issue 18; ISSN 0013-936X
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- United States
- Language:
- English
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