1.16.1.1: mercury(II) reductase
This is an abbreviated version!
For detailed information about mercury(II) reductase, go to the full flat file.
Word Map on EC 1.16.1.1
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1.16.1.1
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organomercurial
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mercury-resistant
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hgcl2
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methylmercury
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lipoamide
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phytoremediation
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mercury-contaminated
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ferrooxidans
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hg-resistant
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geothermal
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metal-resistant
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phenylmercury
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mercury-polluted
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environmental protection
- 1.16.1.1
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organomercurial
-
mercury-resistant
- hgcl2
- methylmercury
- lipoamide
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phytoremediation
-
mercury-contaminated
- ferrooxidans
-
hg-resistant
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geothermal
-
metal-resistant
- phenylmercury
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mercury-polluted
- environmental protection
Reaction
Synonyms
bacterial mercuric reductase, Mer A, MerA, MerA protein, mercurate(II) reductase, mercuric (II) reductase, mercuric ion reductase, mercuric reductase, mercury reductase, Msed_1241, MseMerA, reduced NADP:mercuric ion oxidoreductase, reductase, mercurate(II), Rm CH34, Tn501 MerA, Tn501 mercuric ion reductase
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General Information
General Information on EC 1.16.1.1 - mercury(II) reductase
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evolution
physiological function
additional information
organomercurials are converted to less toxic Hg(0) in the cytosol by the sequential action of organomercurial lyase MerB and mercuric ion reductase MerA, requiring transfer of Hg(II) from MerB to MerA, with transfer to the metallochaperone-like NmerA domain as the kinetically favored pathway in this coevolved system, overview. Hg(II) removal from MerB by the N-terminal domain, NmerA, and catalytic core C-terminal cysteine pairs of its coevolved MerA and by GSH, the major competing cellular thiol in gamma-proteobacteria. The reaction with a 10fold excess of NmerA over HgMerB removes about 92% of Hg(II), while similar extents of reaction require more than 1000fold excess of GSH
evolution
MerA is part of the disulfide oxidoreductase (DSOR) family, are ancient enzymes that have arisen in high temperature environments after the great oxidation event about 2.4 billion years ago
evolution
Metallosphaera sedula ATCC 51363 / DSM 5348 / JCM 9185 / NBRC 15509 / TH2
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MerA is part of the disulfide oxidoreductase (DSOR) family, are ancient enzymes that have arisen in high temperature environments after the great oxidation event about 2.4 billion years ago
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MerA catalyzes the bioconversion of toxic Hg2+ to the least toxic elemental Hg0
physiological function
organomercurials are converted to less toxic Hg(0) in the cytosol by the sequential action of organomercurial lyase MerB and mercuric ion reductase MerA, requiring transfer of Hg(II) from MerB to MerA, with transfer to the metallochaperone-like NmerA domain as the kinetically favored pathway in this coevolved system, overview. Hg(II) removal from MerB by the N-terminal domain, NmerA, and catalytic core C-terminal cysteine pairs of its coevolved MerA and by GSH, the major competing cellular thiol in gamma-proteobacteria. The reaction with a 10fold excess of NmerA over HgMerB removes about 92% of Hg(II), while similar extents of reaction require more than 1000fold excess of GSH. NmerA reacts more completely than GSH with HgMerB
physiological function
the mercuric reductase is functional in high salt, stable at high temperatures, resistant to high concentrations of Hg2, and efficiently detoxifies Hg2 in vivo. Mercuric ion reductase catalyzes the reduction of Hg2+ to Hg0, which is volatile and can be disposed of nonenzymatically
physiological function
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the enzyme catalyzes the reduction and detoxification of toxic mercuric ion, it reduces the Hg(II) ion to the less toxic elemental mercury (Hg(0)) using NADPH as a source of reducing power
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comparison of structural changes upon metal binding in normally appended metal binding proteins: NmerA with and without Hg2+ , PDB entry 2KT3 and 2KT2, respectively
additional information
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MerA is an inducible NADPH-dependent and flavin containing disulfide oxidoreductase enzyme. MerA-encoding plasmid R100-containing Escherichia coli strains are involved in environmental inorganic mercury detoxification
additional information
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many MerA proteins possess metallochaperone-like N-terminal domains (NmerA) that can transfer Hg2+ to the catalytic core domain (Core) for reduction to Hg0. These domains are tethered to the homodimeric core by an about 30-residue linkers that are susceptible to proteolysis, interactions of NmerA and the Core in the full-length protein, structure homology modelling amd structure-function analysis, detailed overview. Binding of Hg2+ to MerA does not alter its hydrodynamic volume
additional information
strain R1-1 is resistant to concentration of over 0.01 mM Hg2+, transforms Hg(II) to Hg(0) during cellular growth, and possesses Hg-dependent NAD(P)H oxidation activities in crude cell extracts that are optimal at temperatures corresponding with the strains' optimal growth temperature of 70°C
additional information
the two acidic residues immediately adjacent to the NmerA metal-binding motif in the ATII-LCL protein have a direct effect on both the halophilicity and catalytic efficiency of the enzyme. Presumably, by increasing the efficiency of delivery of Hg2 ions to the catalytic core for reduction, they also help the host to cope with the high concentrations of mercury present in its hypersaline environment
additional information
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full-length MerA homodimer structure and transfer of Hg(II) from the solvent into the catalytic sites of the MerA core, overview. Enzyme structure-function analysis by molecular dynamics, coarse-grained simulations, small-angle neutron scattering, neutron spin-echo spectroscopy, and dynamic light scattering
additional information
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molecular mechanism of the Hg transfer is analyzed by quantum mechanical/molecular mechanical (QM/MM) calculations. The transfer is nearly thermoneutral and passes through a stable tricoordinated intermediate that is marginally less stable than the two end states. For the overall process, Hg2+ is always paired with at least two thiolates and thus is present at both the C-terminal and catalytic binding sites as a neutral complex. Prior to Hg2+ transfer, C141 is negatively charged. As Hg2+ is transferred into the catalytic site, a proton is transferred from C136 to C559' while C558' becomes negatively charged, resulting in the net transfer of a negative charge over a distance of about 7.5 A. Thus, the transport of this soft divalent cation is made energetically feasible by pairing a competition between multiple Cys thiols and/or thiolates for Hg2+ with a competition between the Hg2+ and protons for the thiolates. Reaction mechansim, formation of a tri-coordinated intermediate state, INT-III, detailed overview
additional information
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the active site is formed by the interaction of the central domain of a subunit with another C-terminal domain. The central domain, described as a pyridine nucleotide oxidoreductase disulfide group, is where catalysis and the transfer of two electrons from NADPH to Hg(II) via FAD, occurs
additional information
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the active site is formed by the interaction of the central domain of a subunit with another C-terminal domain. The central domain, described as a pyridine nucleotide oxidoreductase disulfide group, is where catalysis and the transfer of two electrons from NADPH to Hg(II) via FAD, occurs
additional information
Enterobacter sp. B50C
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the active site is formed by the interaction of the central domain of a subunit with another C-terminal domain. The central domain, described as a pyridine nucleotide oxidoreductase disulfide group, is where catalysis and the transfer of two electrons from NADPH to Hg(II) via FAD, occurs
additional information
Enterobacter sp. A25B
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the active site is formed by the interaction of the central domain of a subunit with another C-terminal domain. The central domain, described as a pyridine nucleotide oxidoreductase disulfide group, is where catalysis and the transfer of two electrons from NADPH to Hg(II) via FAD, occurs
additional information
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the active site is formed by the interaction of the central domain of a subunit with another C-terminal domain. The central domain, described as a pyridine nucleotide oxidoreductase disulfide group, is where catalysis and the transfer of two electrons from NADPH to Hg(II) via FAD, occurs
additional information
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the active site is formed by the interaction of the central domain of a subunit with another C-terminal domain. The central domain, described as a pyridine nucleotide oxidoreductase disulfide group, is where catalysis and the transfer of two electrons from NADPH to Hg(II) via FAD, occurs
additional information
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the active site is formed by the interaction of the central domain of a subunit with another C-terminal domain. The central domain, described as a pyridine nucleotide oxidoreductase disulfide group, is where catalysis and the transfer of two electrons from NADPH to Hg(II) via FAD, occurs
additional information
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the resonance Raman (RR) spectra of various functional forms of MerA are indicative of a modulation of both ring II distortion and H-bonding states of the N5 site and ring III. The Cd(II) binding to the EH2-NADP(H) complexes, biomimetic intermediates in the reaction of Hg(II) reduction, provokes important spectral changes. They are interpreted in terms of flattening of the isoalloxazine ring and large decreases in H-bonding at the N5 site and ring III. The large flexibility of the FAD structure and environment in MerA is in agreement with proposed mechanisms involving C4a(flavin) adducts
additional information
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the active site is formed by the interaction of the central domain of a subunit with another C-terminal domain. The central domain, described as a pyridine nucleotide oxidoreductase disulfide group, is where catalysis and the transfer of two electrons from NADPH to Hg(II) via FAD, occurs
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additional information
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the active site is formed by the interaction of the central domain of a subunit with another C-terminal domain. The central domain, described as a pyridine nucleotide oxidoreductase disulfide group, is where catalysis and the transfer of two electrons from NADPH to Hg(II) via FAD, occurs
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additional information
Pseudomonas entomophila B100A
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the active site is formed by the interaction of the central domain of a subunit with another C-terminal domain. The central domain, described as a pyridine nucleotide oxidoreductase disulfide group, is where catalysis and the transfer of two electrons from NADPH to Hg(II) via FAD, occurs
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