Crystals of isoenzyme 3-3 of rat liver glutathione S-transferase with and without inhibitor

Metalloproteomic approach of mercury-binding proteins in liver and kidney tissues of Plagioscion squamosissimus (corvina) and Colossoma macropomum (tambaqui) from Amazon region: Possible identification of mercury contamination biomarkers

Fish is an important source of protein, vitamins, and minerals. However, this food is also a major source of human exposure to toxic contaminants such as mercury. Thus, this paper aimed to evaluate mercury-binding proteins for possible application as biomarkers of mercury contamination in hepatic and renal tissues of Plagioscion squamosissimus (carnivorous fish) and Colossoma macropomum (omnivorous fish) from the Amazon region using metalloproteomic approach. The proteome of hepatic and renal tissues of fish species was separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), and the mercury concentrations in protein spots were determined by graphite furnace atomic absorption spectrometry (GFAAS). Finally, the protein spots associated to mercury were characterized by electrospray ionization mass spectrometry (ESI-MS/MS). The activity of antioxidant enzymes (SOD, CAT, GPx, and GST) and lipid peroxidation (LPO) were also determined. The results showed that the highest concentrations of mercury were found in the carnivorous species (P. squamosissimus) and that the accumulation pattern of this metal was higher in hepatic tissues than in renal tissues for both species. A tendency was observed for greater enzymatic activity in the hepatic and renal tissues of P. squamosissimus, the species with the highest concentration of mercury. Only GPx activity in the kidney and GST in the liver were lower for the P. squamosissimus species, and this finding can be explained by the interaction of mercury with these enzymes. The data obtained by ESI-MS/MS allowed for the characterization of the protein spots associated to mercury, revealing proteins involved in energy metabolism, biomolecules transport, protein synthesis and degradation, cell differentiation, gene regulation, and the antioxidant system. The results obtained in the present study can contribute to understanding the physiological processes underlying mercury toxicity and have provided new perspectives on possible candidates for mercury contamination biomarkers in fish.

Toxicological effects of methylmercury on walleye (Sander vitreus) and perch (Perca flavescens) from lakes of the boreal forest

Biochemical and physiological responses of walleye (Sander vitreus) and perch (Perca flavescens) were studied in four Canadian boreal forest lakes representing a mercury (Hg) exposure gradient. The aim of this study was to assess the effects of Hg and methylmercury (MeHg) on the general physiological condition of fish as well as to gauge the relationship between MeHg and the glutathione (GSH) system in metal-contaminated and reference sites using a series of biomarkers. Walleye from Lake Malartic had the highest liver MeHg concentrations, exhibited lower hepatosomatic indices (HSI) and lower glutathione S-transferase (GST) activity. HSI was negatively related to liver total Hg concentrations in walleye (R2=0.33, n=108, P<0.0001). Glutathione reductase (GR) and GST activity for walleye from Lake Malartic were related to HSI (R2=0.38, n=25, P=0.0010; R2=0.46, n=27, P<0.0001, respectively). In Lake Desjardins-East, where perch had the highest liver MeHg concentrations, glutathione peroxidase selenium dependent activity (GSH-Px SD) and GST activity were negatively related to liver MeHg concentrations (R2=0.39, n=21, P=0.0026; R2=0.22, n=21, P=0.0298, respectively). This study suggests that Hg may induce adverse effects on the physiology and cellular metabolism of walleye and perch at environmentally relevant concentrations.

X-ray crystal structures of cytosolic glutathione S-transferases. Implications for protein architecture, substrate recognition and catalytic function

Crystal structures of cytosolic glutathione S-transferases (EC 2.5.1.18), complexed with glutathione or its analogues, are reviewed. The atomic models define protein architectural relationships between the different gene classes in the superfamily, and reveal the molecular basis for substrate binding at the two adjacent subsites of the active site. Considerable progress has been made in understanding the mechanism whereby the thiol group of glutathione is destabilized (lowering its pKa) at the active site, a rate-enhancement strategy shared by the soluble glutathione S-transferases.

Baculovirus systems for the expression of human gene products

Significant advances in basic and applied biology have resulted from the use of baculovirus vectors for the expression of heterologous proteins in cultured insect cells and in insect larvae. The development of improved vectors has greatly facilitated the construction of recombinant baculoviruses, both by increasing the efficiency of identifying recombinant viruses and by reducing or eliminating the tedious steps used to purify the desired recombinant virus from its non-recombinant parent virus.