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Literature summary for 1.16.1.1 extracted from

  • Lian, P.; Guo, H.B.; Riccardi, D.; Dong, A.; Parks, J.M.; Xu, Q.; Pai, E.F.; Miller, S.M.; Wei, D.Q.; Smith, J.C.; Guo, H.
    X-ray structure of a Hg2+ complex of mercuric reductase (MerA) and quantum mechanical/molecular mechanical study of Hg2+ transfer between the C-terminal and buried catalytic site cysteine pairs (2014), Biochemistry, 53, 7211-7222 .
    View publication on PubMedView publication on EuropePMC

Crystallization (Commentary)

Crystallization (Comment) Organism
purified recombinanat His-tagged enzyme Tn501 MerA, as NADP+/Hg2+ complex of mutant C136A/C141A, hanging drop vapor diffusion technique, mixing of 0.002 ml of 25 mg/ml protein solution with 0.0.02 ml of reservoir solution containing 0.1 M Tris, pH 9.4, 20 mM NADP+, 2.0 M (NH4)2SO4, equilibration against 0.5 ml of reservoir solution, X-ray diffraction structure determination and analysis at 1.6 A resolution, modeling Pseudomonas aeruginosa

Protein Variants

Protein Variants Comment Organism
C136A/C141A site-directed mutagenesis, the C136A/C141A catalytic core mutant. Mutation of either C136 or C141 or both results in a total loss of Hg2+ reductase activity. CRystal structure determination with bound substrates Pseudomonas aeruginosa

Natural Substrates/ Products (Substrates)

Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
Hg2+ + NADPH Pseudomonas aeruginosa
-
Hg + NADP+ + H+
-
?

Organism

Organism UniProt Comment Textmining
Pseudomonas aeruginosa
-
-
-

Reaction

Reaction Comment Organism Reaction ID
Hg + NADP+ + H+ = Hg2+ + NADPH molecular mechanism of the Hg transfer is analyzed by quantum mechanical/molecular mechanical (QM/MM) calculations, and simulation. 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, detailed overview Pseudomonas aeruginosa

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
Hg2+ + NADPH
-
Pseudomonas aeruginosa Hg + NADP+ + H+
-
?

Subunits

Subunits Comment Organism
homodimer interfacial active site of the MerA homodimer, structure overview Pseudomonas aeruginosa
More structure comparisons of the mutant C136A/C141A (AACC) Hg2+/NADP+ complex (PDB 4K7Z) and the oxidized wild-type (CCCC) enzyme (PDB 1ZK7) Pseudomonas aeruginosa

Synonyms

Synonyms Comment Organism
MerA
-
Pseudomonas aeruginosa
mercuric reductase
-
Pseudomonas aeruginosa
Tn501 MerA
-
Pseudomonas aeruginosa

Cofactor

Cofactor Comment Organism Structure
FAD binding structure, overview Pseudomonas aeruginosa
NADPH
-
Pseudomonas aeruginosa

General Information

General Information Comment Organism
additional information 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 Pseudomonas aeruginosa