Structure of mercuric reductase from Lysinibacillus sphaericus

Experimental Data Snapshot

  • Resolution: 3.48 Å
  • R-Value Free: 0.240 
  • R-Value Work: 0.191 
  • R-Value Observed: 0.194 

Starting Model: experimental
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Structural and functional characterization of mercuric reductase from Lysinibacillus sphaericus strain G1.

Bafana, A.Khan, F.Suguna, K.

(2017) Biometals 30: 809-819

  • DOI: https://doi.org/10.1007/s10534-017-0050-x
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    In response to the widespread presence of inorganic Hg in the environment, bacteria have evolved resistance systems with mercuric reductase (MerA) as the key enzyme. MerA enzymes have still not been well characterized from gram positive bacteria. Current study reports physico-chemical, kinetic and structural characterization of MerA from a multiple heavy metal resistant strain of Lysinibacillus sphaericus, and discusses its implications in bioremediation application. The enzyme was homodimeric with subunit molecular weight of about 60 kDa. The K m and V max were found to be 32 µM of HgCl 2 and 18 units/mg respectively. The enzyme activity was enhanced by β-mercaptoethanol and NaCl up to concentrations of 500 µM and 100 mM respectively, followed by inhibition at higher concentrations. The enzyme showed maximum activity in the pH range of 7-7.5 and temperature range of 25-50 °C, with melting temperature of 67 °C. Cu 2+ exhibited pronounced inhibition of the enzyme with mixed inhibition pattern. The enzyme contained FAD as the prosthetic group and used NADPH as the preferred electron donor, but it showed slight activity with NADH as well. Structural characterization was carried out by circular dichroism spectrophotometry and X-ray crystallography. X-ray confirmed the homodimeric structure of enzyme and gave an insight on the residues involved in catalytic binding. In conclusion, the investigated enzyme showed higher catalytic efficiency, temperature stability and salt tolerance as compared to MerA enzymes from other mesophiles. Therefore, it is proposed to be a promising candidate for Hg 2+ bioremediation.

  • Organizational Affiliation

    Environmental Impact and Sustainability Division, CSIR-NEERI (National Environmental Engineering Research Institute), Nagpur, 440020, India. abafana@rediffmail.com.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Mercuric reductase554Lysinibacillus sphaericusMutation(s): 0 
Gene Names: merA
Find proteins for D9J041 (Lysinibacillus sphaericus)
Explore D9J041 
Go to UniProtKB:  D9J041
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupD9J041
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 3.48 Å
  • R-Value Free: 0.240 
  • R-Value Work: 0.191 
  • R-Value Observed: 0.194 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 236.38α = 90
b = 150.27β = 92.62
c = 122.78γ = 90
Software Package:
Software NamePurpose
iMOSFLMdata reduction
Aimlessdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2017-10-04
    Type: Initial release
  • Version 1.1: 2017-12-06
    Changes: Database references
  • Version 1.2: 2023-11-22
    Changes: Data collection, Database references, Refinement description