Abstract
BackgroundArsenite oxidase (EC 1.20.2.1) is a metalloenzyme that catalyzes the oxidation of arsenite into lesser toxic arsenate. In this study, 78 amino acid sequences of arsenite oxidase from unculturable bacteria available in metagenomic data of arsenic-contaminated soil have been characterized by using standard bioinformatics tools to investigate its phylogenetic relationships, three-dimensional structure and functional parameters. ResultsThe phylogenetic relationship of all arsenite oxidase from unculturable microorganisms was revealed their closeness to bacterial order Rhizobiales. The higher aliphatic content showed that these enzymes are thermostable and could be used for in situ bioremediation. A representative protein from each phylogenetic cluster was analysed for secondary structure arrangements which indicated the presence of α-helices (~63%), β-sheets (57–60%) and turns (13–15%). The validated 3D models suggested that these proteins are hetero-dimeric with two chains whereas alpha chain is the main catalytic subunit which binds with arsenic oxides. Three representative protein models were deposited in Protein Model Database. The query enzymes were predicted with two conserved motifs, one is Rieske 3Fe-4S and the other is molybdopterin protein. ConclusionsComputational analysis of protein interactome revealed the protein partners might be involved in the whole process of arsenic detoxification by Rhizobiales. The overall report is unique to the best of our knowledge, and the importance of this study is to understand the theoretical aspects of the structure and functions of arsenite oxidase in unculturable bacteria residing in arsenic-contaminated sites.
Highlights
Arsenite oxidase (EC 1.20.2.1) is a metalloenzyme that catalyzes the oxidation of arsenite into lesser toxic arsenate
Several metagenomic studies of arsenic-contaminated soil suggested that there is a huge availability of arsenite oxidase in soil bacterium which are unculturable or unexplored to grow in laboratory conditions
Phylogenetic relationship of arsenite oxidase was deduced among uncultured bacterium, and selected strains of known genera which are reported to detoxify arsenic such as Achromobacter sp
Summary
Arsenite oxidase (EC 1.20.2.1) is a metalloenzyme that catalyzes the oxidation of arsenite into lesser toxic arsenate. One of the greatest global threats to human health is arsenic contamination due to its high carcinogenic effect Anthropogenic activities such as mining, agrochemical usage and industrial drainage into water bodies increase the risk of arsenic pollution in soil and water [1,2,3]. Arsenite oxidase has been characterised in several uncultured bacteria in addition to few known bacterial genera such as Aeromonas, Acinetobacter, Alcaligenes, Bosea, Pseudomonas, and Rhizobium, mostly belonging to order Rhizobiales. These microorganisms generate energy deduced from the transition of the oxidation state of arsenic [7,8,9]. The enzymology and genetic evidences of a bacterial process for arsenite oxidation facilitate the scientific approach regarding the arsenic bioremediation by using soil-derived bioactive compounds [13]
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