title: A novel arsenic methyltransferase gene of Westerdykella aurantiaca isolated from arsenic contaminated soil: phylogenetic, physiological, and biochemical studies and its role in arsenic bioremediation.
abstract: Elevated arsenic concentration in the environment and agricultural soil is a serious concern to crop production and human health. Among different detoxification mechanisms, the methylation of arsenic is a widespread phenomenon in nature. A number of microorganisms are able to methylate arsenic, but less is known about the arsenic metabolism in fungi. We identified a novel arsenic methyltransferase (WaarsM) gene from a soil fungus, Westerdykella aurantiaca. WaarsM showed sequence homology with all known arsenic methyltransferases having three conserved SAM binding motifs. The expression of WaarsM enhanced arsenic resistance in E. coli (Δars) and S. cerevisiae (Δacr2) strains by biomethylation and required endogenous reductants, preferably GSH, for methyltransferase activity. The purified WaarsM catalyzes the production of methylated arsenicals from both AsIII and AsV, and also displays AsV reductase activity. It displayed higher methyltransferase activity and lower KM 0.1945 ± 0.021 mM and KM 0.4034 ± 0.078 mM for AsIII and AsV, respectively. S. cerevisiae (Δacr2) cells expressing WaarsM produced 2.2 ppm volatile arsenic and 0.64 ppm DMA(v) with 0.58 ppm volatile arsenicals when exposed to 20 ppm AsV and 2 ppm AsIII, respectively. Arsenic tolerance in rice after co-culture with genetically engineered yeast suggested its potential role in arsenic bioremediation. Thus, characterization of WaarsM provides a potential strategy to reduce arsenic concentration in soil with reduced arsenic accumulation in crops grown in arsenic contaminated areas, and thereby alleviating human health risks.
authors.affiliation: Genetics and Molecular Biology Division, CSIR-National Botanical Research Institute, India. chakrabartyd@nbri.res.in and Department of Biotechnology, Kumaun University, India.
authors.forename: Shikha
authors.initials: S
authors.lastname: Verma
authors.affiliation: Genetics and Molecular Biology Division, CSIR-National Botanical Research Institute, India. chakrabartyd@nbri.res.in and Department of Biotechnology, Kumaun University, India.
authors.forename: Pankaj Kumar
authors.initials: PK
authors.lastname: Verma
authors.affiliation: Environmental Material Division, CSIR-National Environmental Engineering Research Institute, India.
authors.forename: Alok Kumar
authors.initials: AK
authors.lastname: Meher
authors.affiliation: Plant Ecology and Environmental Science Division, CSIR-National Botanical Research Institute, India.
authors.forename: Sanjay
authors.initials: S
authors.lastname: Dwivedi
authors.affiliation: Environmental Material Division, CSIR-National Environmental Engineering Research Institute, India.
authors.forename: Amit Kumar
authors.initials: AK
authors.lastname: Bansiwal
authors.affiliation: Department of Biotechnology, Kumaun University, India.
authors.forename: Veena
authors.initials: V
authors.lastname: Pande
authors.affiliation: Plant Ecology and Environmental Science Division, CSIR-National Botanical Research Institute, India.
authors.forename: Pankaj Kumar
authors.initials: PK
authors.lastname: Srivastava
authors.affiliation: Genetics and Molecular Biology Division, CSIR-National Botanical Research Institute, India. chakrabartyd@nbri.res.in.
authors.forename: Praveen Chandra
authors.initials: PC
authors.lastname: Verma
authors.affiliation: Plant Ecology and Environmental Science Division, CSIR-National Botanical Research Institute, India.
authors.forename: Rudra Deo
authors.initials: RD
authors.lastname: Tripathi
authors.affiliation: Genetics and Molecular Biology Division, CSIR-National Botanical Research Institute, India. chakrabartyd@nbri.res.in.
authors.forename: Debasis
authors.initials: D
authors.lastname: Chakrabarty
mesh_terms: D000595:Amino Acid Sequence; D001151:Arsenic / Q000378:metabolism* / Q000633:toxicity; D055162:Biocatalysis / Q000187:drug effects; D001673:Biodegradation, Environmental / Q000187:drug effects; D003001:Cloning, Molecular; D003198:Computer Simulation; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism; D005658:Fungi / Q000201:enzymology* / Q000235:genetics; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D005800:Genes, Fungal; D005818:Genetic Engineering; D005978:Glutathione / Q000494:pharmacology; D007700:Kinetics; D008745:Methylation; D008780:Methyltransferases / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D012275:Oryza / Q000187:drug effects / Q000378:metabolism; D010802:Phylogeny; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000378:metabolism; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D014170:Transformation, Genetic / Q000187:drug effects; D014835:Volatilization
chemical_list: D012987:Soil; D008780:Methyltransferases; D005978:Glutathione; D001151:Arsenic