Thermal stability of a mercuric reductase from the Red Sea Atlantis II hot brine environment as analyzed by site-directed mutagenesis
Maged M.; Hosseiny A.E.; Saadeldin M.K.; Aziz R.K.; Ramadan E.
Date issued:
2019
Publisher:
American Society for Microbiology
Series Info:
Applied and Environmental Microbiology
85
Type:
Article
Keywords:
Atlantis II
,
Bioprospecting
,
Brine pools
,
Extreme environments
,
MerA
,
Mercuric reductase
,
Protein engineering
,
Red Sea
,
Site-directed mutagenesis
,
Thermostable
,
Amino acids
,
Bioremediation
,
Chemical bonds
,
Detoxification
,
Enzymes
,
Heavy metals
,
Mutagenesis
,
Stability
,
Atlantis
,
Bioprospecting
,
Brine pools
,
Extreme environment
,
MerA
,
Mercuric reductase
,
Protein engineering
,
Red sea
,
Site directed mutagenesis
,
Thermostable
,
Thermodynamic stability
,
bioremediation
,
brine
,
detoxification
,
enzyme
,
enzyme activity
,
genetic analysis
,
heavy metal
,
temperature tolerance
,
Indian Ocean
,
Red Sea [Indian Ocean]
,
bacterial protein
,
mercuric reductase
,
mercury
,
oxidoreductase
,
sea water
,
amino acid sequence
,
bacterium
,
chemistry
,
ecosystem
,
enzyme stability
,
enzymology
,
genetics
,
heat
,
Indian Ocean
,
isolation and purification
,
kinetics
,
metabolism
,
microbiology
,
protein motif
,
sequence alignment
,
site directed mutagenesis
,
Amino Acid Motifs
,
Amino Acid Sequence
,
Bacteria
,
Bacterial Proteins
,
Ecosystem
,
Enzyme Stability
,
Hot Temperature
,
Indian Ocean
,
Kinetics
,
Mercury
,
Mutagenesis, Site-Directed
,
Oxidoreductases
,
Seawater
,
Sequence Alignment
Abstract:
The lower convective layer (LCL) of the Atlantis II brine pool of the Red Sea is a unique environment in terms of high salinity, temperature, and high concentrations of heavy metals. Mercuric reductase enzymes functional in such extreme conditions could be considered a potential tool in the environmental detoxification of mercurial poisoning and might alleviate ecological hazards in the mining industry. Here, we constructed a mercuric reductase library from Atlantis II, from which we identified genes encoding two thermostable mercuric reductase (MerA) isoforms: one is halophilic (designated ATII-LCL) while the other is not (designated ATII-LCLNH). The ATII-LCL MerA has a short motif composed of four aspartic acids (4D414- 417) and two characteristic signature boxes that played a crucial role in its thermal stability. To further understand the mechanism behind the thermostability of the two studied enzymes, we mutated the isoform ATII-LCL-NH and found that the substitution of 2 aspartic acids (2D) at positions 415 and 416 enhanced the thermal stability, while other mutations had the opposite effect. The 2D mutant showed superior thermal tolerance, as it retained 81% of its activity after 10 min of incubation at 70�C. A three-dimensional structure prediction revealed newly formed salt bridges and H bonds in the 2D mutant compared to the parent molecule. To the best of our knowledge, this study is the first to rationally design a mercuric reductase with enhanced thermal stability, which we propose to have a strong potential in the bioremediation of mercurial poisoning. � 2019 American Society for Microbiology.
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