{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,5]],"date-time":"2026-10-05T23:18:36Z","timestamp":1791242316009,"version":"4.1.0"},"reference-count":61,"publisher":"American Society for Microbiology","issue":"9","license":[{"start":{"date-parts":[[2015,5,1]],"date-time":"2015-05-01T00:00:00Z","timestamp":1430438400000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.asm.org\/non-commercial-tdm-license"}],"content-domain":{"domain":["journals.asm.org"],"crossmark-restriction":true},"short-container-title":["Appl Environ Microbiol"],"published-print":{"date-parts":[[2015,5]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n          <jats:p>\n            Methylmercury is a potent neurotoxin that is produced by anaerobic microorganisms from inorganic mercury by a recently discovered pathway. A two-gene cluster, consisting of\n            <jats:italic>hgcA<\/jats:italic>\n            and\n            <jats:italic>hgcB<\/jats:italic>\n            , encodes two of the proteins essential for this activity.\n            <jats:italic>hgcA<\/jats:italic>\n            encodes a corrinoid protein with a strictly conserved cysteine proposed to be the ligand for cobalt in the corrinoid cofactor, whereas\n            <jats:italic>hgcB<\/jats:italic>\n            encodes a ferredoxin-like protein thought to be an electron donor to HgcA. Deletion of either gene eliminates mercury methylation by the methylator\n            <jats:named-content content-type=\"genus-species\">Desulfovibrio desulfuricans<\/jats:named-content>\n            ND132. Here, site-directed mutants of HgcA and HgcB were constructed to determine amino acid residues essential for mercury methylation. Mutations of the strictly conserved residue Cys93 in HgcA, the proposed ligand for the corrinoid cobalt, to Ala or Thr completely abolished the methylation capacity, but a His substitution produced measurable methylmercury. Mutations of conserved amino acids near Cys93 had various impacts on the methylation capacity but showed that the structure of the putative \u201ccap helix\u201d region harboring Cys93 is crucial for methylation function. In the ferredoxin-like protein HgcB, only one of two conserved cysteines found at the C terminus was necessary for methylation, but either cysteine sufficed. An additional, strictly conserved cysteine, Cys73, was also determined to be essential for methylation. This study supports the previously predicted importance of Cys93 in HgcA for methylation of mercury and reveals additional residues in HgcA and HgcB that facilitate the production of this neurotoxin.\n          <\/jats:p>","DOI":"10.1128\/aem.00217-15","type":"journal-article","created":{"date-parts":[[2015,2,28]],"date-time":"2015-02-28T04:09:48Z","timestamp":1425096588000},"page":"3205-3217","update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":83,"title":["Site-Directed Mutagenesis of HgcA and HgcB Reveals Amino Acid Residues Important for Mercury Methylation"],"prefix":"10.1128","volume":"81","author":[{"given":"Steven D.","family":"Smith","sequence":"first","affiliation":[{"name":"Biochemistry Division, University of Missouri, Columbia, Missouri, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Romain","family":"Bridou","sequence":"additional","affiliation":[{"name":"Biochemistry Division, University of Missouri, Columbia, Missouri, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alexander","family":"Johs","sequence":"additional","affiliation":[{"name":"Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jerry M.","family":"Parks","sequence":"additional","affiliation":[{"name":"Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dwayne A.","family":"Elias","sequence":"additional","affiliation":[{"name":"Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA"},{"name":"Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"suffix":"Jr.","given":"Richard 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