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Structure of mercuric reductase from Lysinibacillus sphaericus
Structural highlights
FunctionMERA_LYSSH Resistance to Hg(2+) in bacteria appears to be governed by a specialized system which includes mercuric reductase (By similarity) (PubMed:28894951). MerA protein is responsible for volatilizing mercury as Hg(0) (By similarity) (PubMed:28894951). Catalyzes reduction of Hg(2+) to elemental Hg, which is volatile and can diffuse out of cells passively (PubMed:28894951). Plays a pivotal role in mercury resistance and cell protection (PubMed:28894951).[PIRNR:PIRNR000350][1] Publication Abstract from PubMedIn 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 Km and Vmax were found to be 32 microM of HgCl2 and 18 units/mg respectively. The enzyme activity was enhanced by beta-mercaptoethanol and NaCl up to concentrations of 500 microM 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 degrees C, with melting temperature of 67 degrees C. Cu2+ 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 Hg2+ bioremediation. Structural and functional characterization of mercuric reductase from Lysinibacillus sphaericus strain G1.,Bafana A, Khan F, Suguna K Biometals. 2017 Sep 11. doi: 10.1007/s10534-017-0050-x. PMID:28894951[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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