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Demethylation of methylmercury in bird, fish, and earthworm

April 29, 2021

Toxicity of methylmercury (MeHg) to wildlife and humans results from its binding to cysteine residues of proteins, forming MeHg-cysteinate (MeHgCys) complexes that hinder biological functions. MeHgCys complexes can be detoxified in vivo, yet how this occurs is unknown. We report that MeHgCys complexes are transformed into selenocysteinate (Hg(Sec)4) complexes in multiple animals from two phyla (a waterbird, freshwater fish, and earthworms) sampled in different geographical areas and contaminated by different Hg sources. In addition, high energy-resolution X-ray absorption spectroscopy and chromatography-ICP mass spectrometry of the waterbird liver support the binding of Hg(Sec)4 to selenoprotein P and biomineralization of Hg(Sec)4 to chemically inert nanoparticulate mercury selenide (HgSe). The results provide a foundation for understanding mercury detoxification in higher organisms, and suggest that the identified MeHgCys to Hg(Sec)4 demethylation pathway is common in nature.

Publication Year 2021
Title Demethylation of methylmercury in bird, fish, and earthworm
DOI 10.1021/acs.est.0c04948
Authors Alain Manceau, Jean-Paul Bourdineaud, Ricardo B. Oliveira, Sandra LF Sarrazin, David P. Krabbenhoft, Collin Eagles-Smith, Josh T. Ackerman, Robin Stewart, Christian Ward-Deitrich, M Estela del Castillo Busto, Heidi Goenaga-Infante, Aude Wack, Marius Retegan, Blanka Detlefs, Pieter Glatzel, Paco Bustamante, Kathryn L. Nagy, Brett Poulin
Publication Type Article
Publication Subtype Journal Article
Series Title Environmental Science & Technology
Index ID 70221865
Record Source USGS Publications Warehouse
USGS Organization Forest and Rangeland Ecosys Science Center; Western Ecological Research Center; WMA - Earth System Processes Division