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Journal ArticleDOI

Biochemistry of arsenic detoxification

02 Oct 2002-FEBS Letters (John Wiley & Sons, Ltd)-Vol. 529, Iss: 1, pp 86-92
TL;DR: While the overall schemes for arsenic resistance are similar in prokaryotes and eukaryotes, some of the specific proteins are the products of separate evolutionary pathways.
About: This article is published in FEBS Letters.The article was published on 2002-10-02 and is currently open access. It has received 726 citations till now. The article focuses on the topics: Arsenate reductase activity & Arsenate reductase.
Citations
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Journal ArticleDOI
09 May 2003-Science
TL;DR: This work reviews what is known about arsenic-metabolizing bacteria and their potential impact on speciation and mobilization of arsenic in nature and investigates their role in aquifers.
Abstract: Arsenic is a metalloid whose name conjures up images of murder. Nonetheless, certain prokaryotes use arsenic oxyanions for energy generation, either by oxidizing arsenite or by respiring arsenate. These microbes are phylogenetically diverse and occur in a wide range of habitats. Arsenic cycling may take place in the absence of oxygen and can contribute to organic matter oxidation. In aquifers, these microbial reactions may mobilize arsenic from the solid to the aqueous phase, resulting in contaminated drinking water. Here we review what is known about arsenic-metabolizing bacteria and their potential impact on speciation and mobilization of arsenic in nature.

1,362 citations

Journal ArticleDOI
TL;DR: The purpose of this review is to describe the various cellular and molecular aspects involved in the skin healing process.
Abstract: Regeneration and tissue repair processes consist of a sequence of molecular and cellular events which occur after the onset of a tissue lesion in order to restore the damaged tissue. The exsudative, proliferative, and extracellular matrix remodeling phases are sequential events that occur through the integration of dynamic processes involving soluble mediators, blood cells, and parenchymal cells. Exsudative phenomena that take place after injury contribute to the development of tissue edema. The proliferative stage seeks to reduce the area of tissue injury by contracting myofibroblasts and fibroplasia. At this stage, angiogenesis and reepithelialization processes can still be observed. Endothelial cells are able to differentiate into mesenchymal components, and this difference appears to be finely orchestrated by a set of signaling proteins that have been studied in the literature. This pathway is known as Hedgehog. The purpose of this review is to describe the various cellular and molecular aspects involved in the skin healing process.

873 citations

Journal ArticleDOI
TL;DR: Recent advances in arsenic tolerance are discussed and their potential applications, particularly in the context of multigenic engineering approaches, are discussed.

597 citations

Journal ArticleDOI
TL;DR: Although the adverse health effects arising from exposure to arsenic have been well-recognized, the mechanism(s) of action responsible for the diverse range of health effects are complicated and poorly understood.
Abstract: Arsenic is a trace element found in the earth’s crust at an average concentration of ∼5 μg/g (ppm). Although its relative abundance in the earth’s crust is about 54th, arsenic can become concentrated in some parts of the world because of natural mineralization. Arsenic is a component of 245 minerals, associated most frequently with other metals such as copper, gold, lead, and zinc in sulfidic ores.1−3 When disturbed by natural processes, such as weathering, biological activity, and volcanic eruption, arsenic may be released into the environment. Anthropogenic activities, such as combustion of fossil fuels, mining, ore smelting, and well drilling, also mobilize and introduce arsenic into the environment. Chronic exposure to arsenic from groundwater has been recognized to cause the largest environmental health disaster in the world, putting more than 100 million people at risk of cancer and other arsenic-related diseases.4,5 Because of its prevalence in the environment, potential for human exposure, and the magnitude and severity of health problems it causes, the United States Agency for Toxic Substances and Disease Registry (ATSDR) has ranked arsenic as No. 1 on its Priority List of Hazardous Substances for many years. The recent priority list, posted in 2011 (http://www.atsdr.cdc.gov/SPL/index.html), shows arsenic as No. 1, ahead of lead, mercury, and polychlorinated biphenyls (PCBs). Epidemiological studies of populations exposed to high levels of arsenic due to ingestion from water, including those from Taiwan,6−8 Argentina,9,10 Chile,11,12 West Bengal, India,13,14 Bangladesh,15−17 and Inner Mongolia, China,18,19 have repeatedly shown strong associations between the exposure to high concentrations of arsenic and the prevalence of several cancers,20−23 most severely bladder, lung, and skin cancers. Arsenic is classified as a human carcinogen by the International Agency for Research on Cancer (IARC) and the U.S. Environmental Protection Agency (EPA). Chronic exposure to elevated concentrations of arsenic has also been associated with the increased risk of a number of noncancerous effects.24−27 Although the adverse health effects arising from exposure to arsenic have been well-recognized, the mechanism(s) of action responsible for the diverse range of health effects are complicated and poorly understood.26−30 It is believed that inorganic arsenate (HAsO42-), which is a molecular analogue of phosphate (HPO42-), can compete for phosphate anion transporters and replace phosphate in some biochemical reactions.28 For example, generation of adenosine-5′-triphosphate (ATP) during oxidative phosphorylation can be inhibited by the replacement of phosphate with arsenate. Depletion of ATP by arsenate has been observed in cellular systems.28 However, the replacement of phosphate in DNA by arsenic is not firmly established.31−35 The toxicity of trivalent arsenicals likely occurs through the interaction of trivalent arsenic species with sulfhydryl groups in proteins. Arsenic binding to a specific protein could alter the conformation and function of the protein as well as its recruitment of and interaction with other functional proteins. Therefore, there has been much emphasis on studies of arsenic binding to proteins, for the purpose of understanding arsenic toxicity and developing arsenic-based therapeutics. This review summarizes various aspects of arsenic binding to proteins. It discusses the chemical basis and biological implications and consequences of arsenic binding to proteins. It also describes analytical techniques and the characterization of arsenic binding, including the binding affinity, kinetics, and speciation.

591 citations

Journal ArticleDOI
TL;DR: An analysis of the currently available information on recognized problem areas, and an overview of current knowledge of the principal hydrogeochemical processes of arsenic transportation and transformation are provided, however, a more detailed understanding of local sources of arsenic and mechanisms of arsenic release is required.

589 citations

References
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Journal ArticleDOI
TL;DR: Related sequences in both alpha and beta and in other enzymes that bind ATP or ADP in catalysis help to identify regions contributing to an adenine nucleotide binding fold in both ATP synthase subunits.
Abstract: The alpha- and beta-subunits of membrane-bound ATP synthase complex bind ATP and ADP: beta contributes to catalytic sites, and alpha may be involved in regulation of ATP synthase activity. The sequences of beta-subunits are highly conserved in Escherichia coli and bovine mitochondria. Also alpha and beta are weakly homologous to each other throughout most of their amino acid sequences, suggesting that they have common functions in catalysis. Related sequences in both alpha and beta and in other enzymes that bind ATP or ADP in catalysis, notably myosin, phosphofructokinase, and adenylate kinase, help to identify regions contributing to an adenine nucleotide binding fold in both ATP synthase subunits.

5,191 citations

Journal ArticleDOI
15 Dec 1988-Gene
TL;DR: An approach for performing multiple alignments of large numbers of amino acid or nucleotide sequences is described, based on first deriving a phylogenetic tree from a matrix of all pairwise sequence similarity scores obtained using a fast pairwise alignment algorithm.

3,518 citations

Journal ArticleDOI
TL;DR: In this article, the authors compared sequences and available structures for all the widely distributed representatives of the P-loop GTPases and GTPase-related proteins with the aim of constructing an evolutionary classification for this superclass of proteins and reconstructing the principal events in their evolution.

991 citations

Journal ArticleDOI
TL;DR: It is suggested that trivalent methylated arsenicals, intermediary products of arsenic methylation, may significantly contribute to the adverse effects associated with exposure to iAs, and high methylation capacity does not protect cells from the acute toxicity of triavalent arsenicals.
Abstract: Biomethylation is considered a major detoxification pathway for inorganic arsenicals (iAs). According to the postulated metabolic scheme, the methylation of iAs yields methylated metabolites in which arsenic is present in both pentavalent and trivalent forms. Pentavalent mono- and dimethylated arsenicals are less acutely toxic than iAs. However, little is known about the toxicity of trivalent methylated species. In the work reported here the toxicities of iAs and trivalent and pentavalent methylated arsenicals were examined in cultured human cells derived from tissues that are considered a major site for iAs methylation (liver) or targets for carcinogenic effects associated with exposure to iAs (skin, urinary bladder, and lung). To characterize the role of methylation in the protection against toxicity of arsenicals, the capacities of cells to produce methylated metabolites were also examined. In addition to human cells, primary rat hepatocytes were used as methylating controls. Among the arsenicals examined, trivalent monomethylated species were the most cytotoxic in all cell types. Trivalent dimethylated arsenicals were at least as cytotoxic as trivalent iAs (arsenite) for most cell types. Pentavalent arsenicals were significantly less cytotoxic than their trivalent analogs. Among the cell types examined, primary rat hepatocytes exhibited the greatest methylation capacity for iAs followed by primary human hepatocytes, epidermal keratinocytes, and bronchial epithelial cells. Cells derived from human bladder did not methylate iAs. There was no apparent correlation between susceptibility of cells to arsenic toxicity and their capacity to methylate iAs. These results suggest that (1) trivalent methylated arsenicals, intermediary products of arsenic methylation, may significantly contribute to the adverse effects associated with exposure to iAs, and (2) high methylation capacity does not protect cells from the acute toxicity of trivalent arsenicals.

934 citations

Journal ArticleDOI
TL;DR: It is concluded that the biosynthetic release of LTC4 from cells is mediated by the 190-kDa product of the MRP gene, a primary-active ATP-dependent export pump for conjugates of lipophilic compounds with glutathione and several other anionic residues.

856 citations