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Crystal structures of the organomercurial lyase MerB in its free and mercury-bound forms: insights into the mechanism of methylmercury degradation.

Lafrance-Vanasse J, Lefebvre M, Di Lello P, Sygusch J, Omichinski JG
J Biol Chem 284 938-44 (2009)
Related entries: 3f0o, 3f2f, 3f2g, 3f2h

Cited: 20 times
EuropePMC logo PMID: 19004822

Abstract

Bacteria resistant to methylmercury utilize two enzymes (MerA and MerB) to degrade methylmercury to the less toxic elemental mercury. The crucial step is the cleavage of the carbon-mercury bond of methylmercury by the organomercurial lyase (MerB). In this study, we determined high resolution crystal structures of MerB in both the free (1.76-A resolution) and mercury-bound (1.64-A resolution) states. The crystal structure of free MerB is very similar to the NMR structure, but important differences are observed when comparing the two structures. In the crystal structure, an amino-terminal alpha-helix that is not present in the NMR structure makes contact with the core region adjacent to the catalytic site. This interaction between the amino-terminal helix and the core serves to bury the active site of MerB. The crystal structures also provide detailed insights into the mechanism of carbon-mercury bond cleavage by MerB. The structures demonstrate that two conserved cysteines (Cys-96 and Cys-159) play a role in substrate binding, carbon-mercury bond cleavage, and controlled product (ionic mercury) release. In addition, the structures establish that an aspartic acid (Asp-99) in the active site plays a crucial role in the proton transfer step required for the cleavage of the carbon-mercury bond. These findings are an important step in understanding the mechanism of carbon-mercury bond cleavage by MerB.

Articles - 3f0p mentioned but not cited (5)

  1. Classification of the treble clef zinc finger: noteworthy lessons for structure and function evolution. Kaur G, Subramanian S. Sci Rep 6 32070 (2016)
  2. Expanded Diversity and Phylogeny of mer Genes Broadens Mercury Resistance Paradigms and Reveals an Origin for MerA Among Thermophilic Archaea. Christakis CA, Barkay T, Boyd ES. Front Microbiol 12 682605 (2021)
  3. Direct measurement of mercury(II) removal from organomercurial lyase (MerB) by tryptophan fluorescence: NmerA domain of coevolved γ-proteobacterial mercuric ion reductase (MerA) is more efficient than MerA catalytic core or glutathione . Hong B, Nauss R, Harwood IM, Miller SM. Biochemistry 49 8187-8196 (2010)
  4. Eight Unexpected Selenoprotein Families in Organometallic Biochemistry in Clostridium difficile, in ABC Transport, and in Methylmercury Biosynthesis. Haft DH, Gwadz M. J Bacteriol 205 e0025922 (2023)
  5. Mechanistic pathways of mercury removal from the organomercurial lyase active site. Silva PJ, Rodrigues V. PeerJ 3 e1127 (2015)


Reviews citing this publication (2)

  1. Bacterial mer operon-mediated detoxification of mercurial compounds: a short review. Mathema VB, Thakuri BC, Sillanpää M. Arch Microbiol 193 837-844 (2011)
  2. Demethylation-The Other Side of the Mercury Methylation Coin: A Critical Review. Barkay T, Gu B. ACS Environ Au 2 77-97 (2022)

Articles citing this publication (13)

  1. Site-directed mutagenesis of HgcA and HgcB reveals amino acid residues important for mercury methylation. Smith SD, Bridou R, Johs A, Parks JM, Elias DA, Hurt RA, Brown SD, Podar M, Wall JD. Appl Environ Microbiol 81 3205-3217 (2015)
  2. The MerE protein encoded by transposon Tn21 is a broad mercury transporter in Escherichia coli. Kiyono M, Sone Y, Nakamura R, Pan-Hou H, Sakabe K. FEBS Lett 583 1127-1131 (2009)
  3. Structural characterization of intramolecular Hg(2+) transfer between flexibly linked domains of mercuric ion reductase. Johs A, Harwood IM, Parks JM, Nauss RE, Smith JC, Liang L, Miller SM. J Mol Biol 413 639-656 (2011)
  4. Synthesis, structure, and reactivity of two-coordinate mercury alkyl compounds with sulfur ligands: relevance to mercury detoxification. Melnick JG, Yurkerwich K, Parkin G. Inorg Chem 48 6763-6772 (2009)
  5. Protolytic cleavage of Hg-C bonds induced by 1-methyl-1,3-dihydro-2H-benzimidazole-2-selone: synthesis and structural characterization of mercury complexes. Palmer JH, Parkin G. J Am Chem Soc 137 4503-4516 (2015)
  6. Mercurial-resistance determinants in Pseudomonas strain K-62 plasmid pMR68. Sone Y, Mochizuki Y, Koizawa K, Nakamura R, Pan-Hou H, Itoh T, Kiyono M. AMB Express 3 41 (2013)
  7. Organic and inorganic mercurials have distinct effects on cellular thiols, metal homeostasis, and Fe-binding proteins in Escherichia coli. LaVoie SP, Mapolelo DT, Cowart DM, Polacco BJ, Johnson MK, Scott RA, Miller SM, Summers AO. J Biol Inorg Chem 20 1239-1251 (2015)
  8. High Efficiency Mercury Sorption by Dead Biomass of Lysinibacillus Sphaericus-New Insights into the Treatment of Contaminated Water. Vega-Páez JD, Rivas RE, Dussán-Garzón J. Materials (Basel) 12 E1296 (2019)
  9. Toward Bioremediation of Methylmercury Using Silica Encapsulated Escherichia coli Harboring the mer Operon. Kane AL, Al-Shayeb B, Holec PV, Rajan S, Le Mieux NE, Heinsch SC, Psarska S, Aukema KG, Sarkar CA, Nater EA, Gralnick JA. PLoS One 11 e0147036 (2016)
  10. Transcriptomic evidence for versatile metabolic activities of mercury cycling microorganisms in brackish microbial mats. Vigneron A, Cruaud P, Aubé J, Guyoneaud R, Goñi-Urriza M. NPJ Biofilms Microbiomes 7 83 (2021)
  11. Dimethylmercury Degradation by Dissolved Sulfide and Mackinawite. West J, Graham AM, Liem-Nguyen V, Jonsson S. Environ Sci Technol 54 13731-13738 (2020)
  12. Structural and Biochemical Characterization of Organotin and Organolead Compounds Binding to the Organomercurial Lyase MerB Provide New Insights into Its Mechanism of Carbon-Metal Bond Cleavage. Wahba HM, Stevenson MJ, Mansour A, Sygusch J, Wilcox DE, Omichinski JG. J Am Chem Soc 139 910-921 (2017)
  13. Cytoprotective effects of imidazole-based [S1] and [S2]-donor ligands against mercury toxicity: a bioinorganic approach. Karri R, Chalana A, Das R, Rai RK, Roy G. Metallomics 11 213-225 (2019)


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