title: Molecular mechanisms of how mercury inhibits water permeation through aquaporin-1: understanding by molecular dynamics simulation.
abstract: Aquaporin (AQP) functions as a water-conducting pore. Mercury inhibits the water permeation through AQP. Although site-directed mutagenesis has shown that mercury binds to Cys189 during the inhibition process, it is not fully understood how this inhibits the water permeation through AQP1. We carried out 40 ns molecular dynamics simulations of bovine AQP1 tetramer with mercury (Hg-AQP1) or without mercury (Free AQP1). In Hg-AQP1, Cys191 (Cys189 in human AQP1) is converted to Cys-SHg+ in each monomer. During each last 10 ns, we observed water permeation events occurred 23 times in Free AQP1 and never in Hg-AQP1. Mercury binding did not influence the whole structure, but did induce a collapse in the orientation of several residues at the ar/R region. In Free AQP1, backbone oxygen atoms of Gly190, Cys191, and Gly192 lined, and were oriented to, the surface of the water pore channel. In Hg-AQP1, however, the SHg+ of Cys191-SHg+ was oriented toward the outside of the water pore. As a result, the backbone oxygen atoms of Gly190, Cys191, and Gly192 became disorganized and the ar/R region collapsed, thereby obstructing the permeation of water. We suggest that mercury disrupts the water pore of AQP1 through local conformational changes in the ar/R region.
authors.affiliation: Department of Pharmacology, School of Medicine, Keio University, Shinjuku-ku, Tokyo, Japan. hirano@riken.jp
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Hirano
authors.forename: Noriaki
authors.initials: N
authors.lastname: Okimoto
authors.forename: Ikuko
authors.initials: I
authors.lastname: Kadohira
authors.forename: Makoto
authors.initials: M
authors.lastname: Suematsu
authors.forename: Kenji
authors.initials: K
authors.lastname: Yasuoka
authors.forename: Masato
authors.initials: M
authors.lastname: Yasui
mesh_terms: D000818:Animals; D051398:Aquaporin 1 / Q000737:chemistry / Q000378:metabolism*; D001696:Biomechanical Phenomena / Q000187:drug effects; D002417:Cattle; D003545:Cysteine / Q000378:metabolism; D008628:Mercury / Q000494:pharmacology*; D056004:Molecular Dynamics Simulation; D010539:Permeability / Q000187:drug effects; D016062:Porosity / Q000187:drug effects; D017433:Protein Structure, Secondary; D014867:Water / Q000737:chemistry / Q000378:metabolism*
chemical_list: D014867:Water; D051398:Aquaporin 1; D008628:Mercury; D003545:Cysteine
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