Toxic hexavalent chromium (Cr⁶⁺) released during various industrial and mining processes leads to serious environmental problems and health hazards. Cr⁶⁺ compounds are known to be highly toxic, mutagenic, teratogenic, and carcinogenic. Microorganisms such as bacteria employ various resistance mechanisms such as ion transport (efflux), reduction, DNA repair, and so on to overcome chromate toxicity. The genes responsible for such activity are either located in chromosome or in the plasmid of bacteria. In total of 2557 chromate resistance genes found in bacteria (2,368), eukarya (171), and archea (18) have been retrieved from the National Center for Biotechnology Information (NCBI) gene database obtained from both culture-dependent and -independent methods and were analyzed for their function, location, and diversification. Further proteomic analysis revealed a hydrophobic membrane protein such as ChrA belong to the chromate ion transporter (CHR) superfamily found to be involved in efflux of chromate ion from the cell cytoplasm conferring chromate resistance in bacteria were retrieved from the NCBI database and categorized in two groups of monodomain proteins with a sequence length of 123–234 amino acids, called bacterial short-chain CHR (bacterial SCHR), and bidomain proteins with a sequence length of 345–495 amino acids, called bacterial long-chain CHR (bacterial LCHR). Phylogenetic divergence study of 237 LCHR and 121 SCHR proteins was conducted using the neighbor-joining method in MEGA6.0 and found to be clustered into four and six clusters, respectively. Apart from CHR superfamily, various groups of oxidoreductase enzymes such as chromate reductase, nitroreductase, iron reductase, quinone reductase, hydrogenase, flavin reductase, and nicotinamide adenine dinucleotide phosphate (NADPH)–dependent reductase showing potential toward reduction of chromate have also been identified in different microorganisms. Comparative structural analyses of seven well-studied enzymes involved in chromate reduction from Protein Data Bank database were categorized either NADPH-dependent flavin mononucleotide (FMN) reductase or FMN-dependent nitroreductase. In spite of structural diversity (e.g., tetramer/dimer, arrangements of helices/sheets/coils) all are found to be involved in chromate reduction. Chromate reductions mediated by transfer of electron from nicotinamide adenine dinucleotide to various substrates (electron acceptor such as chromate) through FMN cofactor. The anchoring amino acid residues such as Glu, Tyr, Ser, Asn, Phe and Arg interact with FMN in NADPH-dependent FMN reductases but Gly, Arg, and Ser are the interacting residues in FMN-dependent nitroreductase. Enzyme-specific domains such as PF00724, PF03358, and PF00881 are present in these enzymes. The enzymes with known structures and functions can be easily manipulated through protein engineering approach for potential applications.

Oxidative modifications in proteins can participate in the regulation of cellular functions and are frequently observed in numerous states of diseases. Albumin can undergo increased glycation during diabetes. An accumulation of oxidatively modified proteins in human mature adipocytes incubated with glycated albumin has previously been described. This study herein reports the identification of specifically carbonylated targets following separation of the cell proteins by 2D gels, Western blotting and mass spectrometry analyses. It identified eight oxidatively modified proteins, two of which (ACTB and Annexin A2) appeared as significantly more carbonylated in adipocytes treated with glycated albumin than with native albumin. Intracellular stress, evaluated in SW872 cell line, showed an impairment in the protective antioxidant action exerted by native BSA after the glycation of the protein. Decreased proteasome peptidase activities were found in glycated BSA-treated mature adipocytes. The data suggest an association of oxidative damage with the progression of diabetes disorders at the adipocytes level.

The aquatic environment provides a sink for the environmental pollutants that have potential to induce oxidative stress by altering neurobehavioral response of aquatic animals. Benzo[a]pyrene (B[a]P), a polycyclic aromatic hydrocarbon is known to induce oxidative stress in the brain. Withania somnifera has been used traditionally for its neuroprotective effect in experimental models of neurological disorders. The present study is aimed to evaluate the neuroprotective potential of Withania somnifera leaf extract (WSLE) following exposure to waterborne B[a]P. Wild-type zebrafish (Danio rerio) were designated as naive, control (dimethyl sulfoxide), WSLE, B[a]P, and B[a]P + WSLE groups. Behavioral studies showed reversal in scototaxis (anxiety-like) behavior in B[a]P group and was restored by WSLE cosupplementation in B[a]P + WSLE group. B[a]P-induced altered antioxidant status was ameliorated by WSLE in the B[a]P + WSLE group. Previous studies showed that the periventricular gray zone (PGZ) of the optic tectum in zebrafish brain regulates scototaxis (anxiety-like) behavior. Our histopathological observation showed a significant increase in the pyknotic neuronal counts in PGZ of the B[a]P group and was ameliorated by WSLE cosupplementation. The study showed that the reversal in scototaxis behavior following exposure to waterborne B[a]P might be associated with neuromorphological alterations in PGZ, whereas a pioneer ethnopharmacological approach of WSLE cosupplementation showed its neuroprotective role to restore normal scototaxis of zebrafish. Future research directing toward understanding the role of visual circuit involved with impaired scototaxis behavior in zebrafish might provide new pathological outcomes following exposure to B[a]P.