Resistance to mercuric ions in bacteria is conferred by mercuric reductase, which reduces Hg(II) to Hg(0) in the cytoplasmic compartment. Specific mercuric ion transport systems exist to take up Hg(II) salts and deliver them to the active site of the reductase. This short review discusses the role of transport proteins in resistance and the mechanism of transfer of Hg(II) between the mercury-re...

Mercuric ion reductase (MerA), a mercury detoxification enzyme, has been tuned by evolution to have high specificity for mercuric ions (Hg(2+)) and to catalyze their reduction to a more volatile, less toxic elemental form. Here, we present a biochemical and structural characterization of MerA from the thermophilic crenarchaeon Metallosphaera sedula. MerA from M. sedula is a thermostable enzyme,...

Introduction The flavoprotein disulphide oxidoreductases constitute a growing family of homologous dimeric enzymes, with an important and diverse range of functions in vivo. Among its members are dihydrolipoyl dehydrogenase, glutathione reductase, mercuric reductase, thioredoxin reductase, trypanothione reductase and a related enzyme, NADPH peroxidase (for recent reviews of their structures and...

Thioredoxin reductase (EC 1.6.4.5) is a widely distributed flavoprotein that catalyzes the NADPH-dependent reduction of thioredoxin. Thioredoxin plays several key roles in maintaining the redox environment of the cell. Like all members of the enzyme family that includes lipoamide dehydrogenase, glutathione reductase and mercuric reductase, thioredoxin reductase contains a redox active disulfide...

The NADPH:2-ketopropyl-coenzyme M oxidoreductase/carboxylase (2-KPCC) is the terminal enzyme in a metabolic pathway that results in the conversion of propylene to the central metabolite acetoacetate in Xanthobacter autotrophicus Py2. This enzyme is an FAD-containing enzyme that is a member of the NADPH:disulfide oxidoreductase (DSOR) family of enzymes that include glutathione reductase, dihydro...

In a continuing effort to analyze the selectivity/redundancy of the three glutaredoxin (Grx) enzymes of the model cyanobacterium Synechocystis PCC6803, we have characterized an enzyme system that plays a crucial role in protection against two toxic metal pollutants, mercury and uranium. The present data show that Grx1 (Slr1562 in CyanoBase) selectively interacts with the presumptive mercuric re...

The flavoenzyme mercuric ion reductase from Bacillus sp. strain RC607 was purified by dye-ligand affinity chromatography. The protein was crystallized from solutions of high ionic strength, and one of the two crystal forms obtained has proven suitable for x-ray diffraction studies. Preliminary analysis showed that these crystals belong to the tetragonal space group 1422. The unit cell dimension...

Bacteria mediate resistance to organomercurial and inorganic mercuric salts by metabolic conversion to nontoxic elemental mercury, Hg(0). The genes responsible for mercury resistance are organized in the mer operon, and such operons are often found in plasmids that also bear drug resistance determinants. We have subcloned three of these mer genes, merR, merB, and merA, and have studied their pr...

mercury is one of the three major environmental metal poisons, and mercuric chloride is a highly reactive compound which can harm cells by a variety of mechanisms including direct interaction with sulphydryl groups of proteins and enzymes, therefore affecting the enzymatic activity. this study focused on the effect of hg++ on horseradish peroxidase (donor: hydrogen peroxide oxidoreductase, ec 1...