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Salem MA, Nour El-Din HT, Hashem AM, Aziz RK. Genome-Scale Investigation of the Regulation of azoR Expression in Escherichia coli Using Computational Analysis and Transposon Mutagenesis. MICROBIAL ECOLOGY 2024; 87:63. [PMID: 38691135 PMCID: PMC11062982 DOI: 10.1007/s00248-024-02380-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Accepted: 04/12/2024] [Indexed: 05/03/2024]
Abstract
Bacterial azoreductases are enzymes that catalyze the reduction of ingested or industrial azo dyes. Although azoreductase genes have been well identified and characterized, the regulation of their expression has not been systematically investigated. To determine how different factors affect the expression of azoR, we extracted and analyzed transcriptional data from the Gene Expression Omnibus (GEO) resource, then confirmed computational predictions by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Results showed that azoR expression was lower with higher glucose concentration, agitation speed, and incubation temperature, but higher at higher culture densities. Co-expression and clustering analysis indicated ten genes with similar expression patterns to azoR: melA, tpx, yhbW, yciK, fdnG, fpr, nfsA, nfsB, rutF, and chrR (yieF). In parallel, constructing a random transposon library in E. coli K-12 and screening 4320 of its colonies for altered methyl red (MR)-decolorizing activity identified another set of seven genes potentially involved in azoR regulation. Among these genes, arsC, relA, plsY, and trmM were confirmed as potential azoR regulators based on the phenotypic decolorization activity of their transposon mutants, and the expression of arsC and relA was confirmed, by qRT-PCR, to significantly increase in E. coli K-12 in response to different MR concentrations. Finally, the significant decrease in azoR transcription upon transposon insertion in arsC and relA (as compared to its expression in wild-type E. coli) suggests their probable involvement in azoR regulation. In conclusion, combining in silico analysis and random transposon mutagenesis suggested a set of potential regulators of azoR in E. coli.
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Affiliation(s)
- Mona A Salem
- Department of Microbiology, Faculty of Pharmacy, The British University in Egypt (BUE), 11837, El-Sherouk City, Egypt
| | - Hanzada T Nour El-Din
- Department of Microbiology and Immunology, Faculty of Pharmacy, Cairo University, Qasr El-Ainy St, 11562, Cairo, Egypt
| | - Abdelgawad M Hashem
- Department of Microbiology, Faculty of Pharmacy, The British University in Egypt (BUE), 11837, El-Sherouk City, Egypt
| | - Ramy K Aziz
- Department of Microbiology and Immunology, Faculty of Pharmacy, Cairo University, Qasr El-Ainy St, 11562, Cairo, Egypt.
- Center for Genome and Microbiome Research, Cairo University, 11562, Cairo, Egypt.
- Microbiology and Immunology Research Program, Children's Cancer Hospital Egypt, 57357, 11617, Cairo, Egypt.
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2
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Foley MH, Walker ME, Stewart AK, O'Flaherty S, Gentry EC, Patel S, Beaty VV, Allen G, Pan M, Simpson JB, Perkins C, Vanhoy ME, Dougherty MK, McGill SK, Gulati AS, Dorrestein PC, Baker ES, Redinbo MR, Barrangou R, Theriot CM. Bile salt hydrolases shape the bile acid landscape and restrict Clostridioides difficile growth in the murine gut. Nat Microbiol 2023; 8:611-628. [PMID: 36914755 PMCID: PMC10066039 DOI: 10.1038/s41564-023-01337-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Accepted: 02/08/2023] [Indexed: 03/16/2023]
Abstract
Bile acids (BAs) mediate the crosstalk between human and microbial cells and influence diseases including Clostridioides difficile infection (CDI). While bile salt hydrolases (BSHs) shape the BA pool by deconjugating conjugated BAs, the basis for their substrate selectivity and impact on C. difficile remain elusive. Here we survey the diversity of BSHs in the gut commensals Lactobacillaceae, which are commonly used as probiotics, and other members of the human gut microbiome. We structurally pinpoint a loop that predicts BSH preferences for either glycine or taurine substrates. BSHs with varying specificities were shown to restrict C. difficile spore germination and growth in vitro and colonization in pre-clinical in vivo models of CDI. Furthermore, BSHs reshape the pool of microbial conjugated bile acids (MCBAs) in the murine gut, and these MCBAs can further restrict C. difficile virulence in vitro. The recognition of conjugated BAs by BSHs defines the resulting BA pool, including the expansive MCBAs. This work provides insights into the structural basis of BSH mechanisms that shape the BA landscape and promote colonization resistance against C. difficile.
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Affiliation(s)
- Matthew H Foley
- Department of Pathobiology and Population Health, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA
- Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Raleigh, NC, USA
| | - Morgan E Walker
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Allison K Stewart
- Department of Chemistry, North Carolina State University, Raleigh, NC, USA
| | - Sarah O'Flaherty
- Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Raleigh, NC, USA
| | - Emily C Gentry
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, San Diego, CA, USA
- Collaborative Mass Spectrometry Innovation Center, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA
| | - Shakshi Patel
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Violet V Beaty
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Garrison Allen
- Department of Pathobiology and Population Health, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA
| | - Meichen Pan
- Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Raleigh, NC, USA
| | - Joshua B Simpson
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Caroline Perkins
- Department of Pathobiology and Population Health, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA
| | - Molly E Vanhoy
- Department of Pathobiology and Population Health, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA
| | - Michael K Dougherty
- Department of Pediatrics, Division of Gastroenterology and Hepatology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Sarah K McGill
- Department of Pediatrics, Division of Gastroenterology and Hepatology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Ajay S Gulati
- Department of Pediatrics, Division of Gastroenterology and Hepatology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Pieter C Dorrestein
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, San Diego, CA, USA
- Collaborative Mass Spectrometry Innovation Center, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA
| | - Erin S Baker
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Department of Chemistry, North Carolina State University, Raleigh, NC, USA
| | - Matthew R Redinbo
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
- Departments of Biochemistry and Biophysics, and Microbiology and Immunology, and the Integrated Program in Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
| | - Rodolphe Barrangou
- Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Raleigh, NC, USA.
| | - Casey M Theriot
- Department of Pathobiology and Population Health, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA.
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3
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Simpson JB, Sekela JJ, Carry BS, Beaty V, Patel S, Redinbo MR. Diverse but desolate landscape of gut microbial azoreductases: A rationale for idiopathic IBD drug response. Gut Microbes 2023; 15:2203963. [PMID: 37122075 PMCID: PMC10132220 DOI: 10.1080/19490976.2023.2203963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 02/01/2023] [Accepted: 04/04/2023] [Indexed: 05/02/2023] Open
Abstract
Prodrugs reliant on microbial activation are widely used but exhibit a range of efficacies that remain poorly understood. The anti-inflammatory compound 5-aminosalicylic acid (5-ASA), which is packaged in a variety of azo-linked prodrugs provided to most Ulcerative Colitis (UC) patients, shows confounding inter-individual variabilities in response. Such prodrugs must be activated by azo-bond reduction to form 5-ASA, a process that has been attributed to both enzymatic and non-enzymatic catalysis. Gut microbial azoreductases (AzoRs) are the first catalysts shown to activate azo-linked drugs and to metabolize toxic azo-chemicals. Here, we chart the scope of the structural and functional diversity of AzoRs in health and in patients with the inflammatory bowel diseases (IBDs) UC and Crohn's Disease (CD). Using structural metagenomics, we define the landscape of gut microbial AzoRs in 413 healthy donor and 1059 IBD patient fecal samples. Firmicutes encode a significantly higher number of unique AzoRs compared to other phyla. However, structural and biochemical analyses of distinct AzoRs from the human microbiome reveal significant differences between prevalent orthologs in the processing of toxic azo-dyes, and their generally poor activation of IBD prodrugs. Furthermore, while individuals with IBD show higher abundances of AzoR-encoding gut microbial taxa than healthy controls, the overall abundance of AzoR-encoding microbes is markedly low in both disease and health. Together, these results establish that gut microbial AzoRs are functionally diverse but sparse in both health and disease, factors that may contribute to non-optimal processing of azo-linked prodrugs and idiopathic IBD drug responses.
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Affiliation(s)
- Joshua B. Simpson
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Josh J. Sekela
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Benjamin S. Carry
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Violet Beaty
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Shakshi Patel
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Matthew. R. Redinbo
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Department of Biochemistry and Biophysics, Department of Microbiology and Immunology, and the Integrated Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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Liu J, Zhang D, Luo Y, Ding T, Hu L. Microbial mediated arsenate reducing behavior in landfill leachate-saturated zone. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 314:120281. [PMID: 36167165 DOI: 10.1016/j.envpol.2022.120281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 09/19/2022] [Accepted: 09/22/2022] [Indexed: 06/16/2023]
Abstract
As(V) reduction mediated by microorganisms might be an essential process in resisting As toxicity since As(V) is the major species in the landfill. LSZ has been considered as a trigger of all types of microbial activity inside a landfill site. This research investigated the microbial As(V)-reducing behavior in LSZ. The results revealed that higher As(V)-reduction efficiency in higher As(V) content-stress LSZ scenario. The corresponding microbial diversity also varied with the As(V) content. The microbial community structure was related to arrA and arsC distribution, which encode respiratory As(V) reductase and cytoplasmic As(V) reductase, respectively. The landfill As bio-reduction pathways were modeled, as well as the As functional gene distribution among different As(V) contents at different landfill stages. The C, N, and S metabolic processes generally affected the As(V)-resistance genes distribution. Thiosulfate oxidation, denitrification, and dissimilatory nitrate reduction positively affected arsC, while dissimilatory sulfate reduction and methanogenesis trended to play a negative role. This research provides new insight into As(V) bio-reduction inside a landfill site in terms of functional genes distribution and correlation with nutrient elements metabolic processes.
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Affiliation(s)
- Jinbao Liu
- Zhejiang Tongji Vocational College of Science and Technology, Hangzhou, 311231, China
| | - Dongchen Zhang
- College of Quality and Safety Engineering, Institution of Industrial Carbon Metrology, China Jiliang University, Hangzhou, 310018, China
| | - Yongjun Luo
- Zhejiang Guangchuan Engineering Consulting Co. Ltd., Hangzhou, Zhejiang, 310020, China
| | - Tao Ding
- College of Quality and Safety Engineering, Institution of Industrial Carbon Metrology, China Jiliang University, Hangzhou, 310018, China
| | - Lifang Hu
- College of Quality and Safety Engineering, Institution of Industrial Carbon Metrology, China Jiliang University, Hangzhou, 310018, China.
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Song D, Zhu S, Chen L, Zhang T, Zhang L. The strategy of arsenic metabolism in an arsenic-resistant bacterium Stenotrophomonas maltophilia SCSIOOM isolated from fish gut. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 312:120085. [PMID: 36058313 DOI: 10.1016/j.envpol.2022.120085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 08/04/2022] [Accepted: 08/29/2022] [Indexed: 06/15/2023]
Abstract
Bacteria are candidates for the biotransformation of environmental arsenic (As), while As metabolism in bacteria is not yet fully understood. In this study, we sequenced the genome of an As-resistant bacterium strain Stenotrophomonas maltophilia SCSIOOM isolated from the fish gut. After arsenate (As(V)) exposure, S. maltophilia transformed As(V) to organoarsenicals, along with the significant change of the expression of 40 genes, including the upregulation of arsH, arsRBC and betIBA. The heterogeneous expression of arsH and arsRBC increased As resistance of E. coli AW3110 by increasing As efflux and transformation. E. coli AW3110 (pET-betIBA) could transform inorganic As into dimethylarsinate (DMA) and nontoxic arsenobetaine (AsB), which suggested that AsB could be synthesized through the synthetic pathway of its analog-glycine betaine. In addition, the existence of arsRBC, betIBA and arsH reduced the reactive oxygen species (ROS) induced by As exposure. In total, these results demonstrated that S. maltophilia adopted an As metabolism strategy by reducing As accumulation and synthesizing less toxic As species. We first reported the production and potential synthetic pathway of AsB in bacteria, which improved our knowledge of As toxicology in microorganisms.
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Affiliation(s)
- Dongdong Song
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Siqi Zhu
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Lizhao Chen
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China; Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, 511458, China
| | - Ting Zhang
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China; Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, 511458, China
| | - Li Zhang
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China; Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, 511458, China; Innovation Academy of South China Sea Ecology and Environmental Engineering, Chinese Academy of Sciences, Guangzhou, 510301, China.
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6
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Sedláček V, Kryl M, Kučera I. The ArsH Protein Product of the Paracoccus denitrificans ars Operon Has an Activity of Organoarsenic Reductase and Is Regulated by a Redox-Responsive Repressor. Antioxidants (Basel) 2022; 11:antiox11050902. [PMID: 35624766 PMCID: PMC9137774 DOI: 10.3390/antiox11050902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 04/28/2022] [Accepted: 04/29/2022] [Indexed: 01/25/2023] Open
Abstract
Paracoccus denitrificans ArsH is encoded by two identical genes located in two distinct putative arsenic resistance (ars) operons. Escherichia coli-produced recombinant N-His6-ArsH was characterized both structurally and kinetically. The X-ray structure of ArsH revealed a flavodoxin-like domain and motifs for the binding of flavin mononucleotide (FMN) and reduced nicotinamide adenine dinucleotide phosphate (NADPH). The protein catalyzed FMN reduction by NADPH via ternary complex mechanism. At a fixed saturating FMN concentration, it acted as an NADPH-dependent organoarsenic reductase displaying ping-pong kinetics. A 1:1 enzymatic reaction of phenylarsonic acid with the reduced form of FMN (FMNH2) and formation of phenylarsonous acid were observed. Growth experiments with P. denitrificans and E. coli revealed increased toxicity of phenylarsonic acid to cells expressing arsH, which may be related to in vivo conversion of pentavalent As to more toxic trivalent form. ArsH expression was upregulated not only by arsenite, but also by redox-active agents paraquat, tert-butyl hydroperoxide and diamide. A crucial role is played by the homodimeric transcriptional repressor ArsR, which was shown in in vitro experiments to monomerize and release from the DNA-target site. Collectively, our results establish ArsH as responsible for enhancement of organo-As(V) toxicity and demonstrate redox control of ars operon.
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A comparative study indicates vertical inheritance and horizontal gene transfer of arsenic resistance-related genes in eukaryotes. Mol Phylogenet Evol 2022; 173:107479. [DOI: 10.1016/j.ympev.2022.107479] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 02/10/2022] [Accepted: 04/05/2022] [Indexed: 12/27/2022]
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Identification and Genome Analysis of an Arsenic-Metabolizing Strain of Citrobacter youngae IITK SM2 in Middle Indo-Gangetic Plain Groundwater. BIOMED RESEARCH INTERNATIONAL 2022; 2022:6384742. [PMID: 35309170 PMCID: PMC8930248 DOI: 10.1155/2022/6384742] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 02/18/2022] [Accepted: 02/21/2022] [Indexed: 11/17/2022]
Abstract
Whole-genome sequencing (WGS) data of a bacterial strain IITK SM2 isolated from an aquifer located in the middle Indo-Gangetic plain is reported here, along with its physiological, morphological, biochemical, and redox-transformation characteristics in the presence of dissolved arsenic (As). The aquifer exhibits oxidizing conditions relative to As speciation. Analyses based on 16S rRNA and recN sequences indicate that IITK SM2 was clustered with C. youngae NCTC 13708T and C. pasteuri NCTC UMH17T. However, WGS analyses using the digital DNA-DNA hybridization and Rapid Annotations using Subsystems Technology suggest that IITK SM2 belongs to a strain of C. youngae. This strain can effectively reduce As(V) to As(III) but cannot oxidize As(III) to As(V). It exhibited high resistance to As(V) [32,000 mg L-1] and As(III) [1,100 mg L-1], along with certain other heavy metals typically found in contaminated groundwater. WGS analysis also indicates the presence of As-metabolizing genes such as arsC, arsB, arsA, arsD, arsR, and arsH in this strain. Although these genes have been identified in several As(V)-reducers, the clustering of these genes in the forms of arsACBADR, arsCBRH, and an independent arsC gene has not been observed in any other Citrobacter species or other selected As(V)-reducing strains of Enterobacteriaceae family. Moreover, there were differences in the number of genes corresponding to membrane transporters, virulence and defense, motility, protein metabolism, phages, prophages, and transposable elements in IITK SM2 when compared to other strains. This genomic dataset will facilitate subsequent molecular and biochemical analyses of strain IITK SM2 to identify the reasons for high arsenic resistance in Citrobacter youngae and understand its role in As mobilization in middle Indo-Gangetic plain aquifers.
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Shi K, Radhakrishnan M, Dai X, Rosen BP, Wang G. NemA Catalyzes Trivalent Organoarsenical Oxidation and Is Regulated by the Trivalent Organoarsenical-Selective Transcriptional Repressor NemR. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:6485-6494. [PMID: 33851826 PMCID: PMC8879406 DOI: 10.1021/acs.est.1c00574] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Synthetic aromatic arsenicals such as roxarsone (Rox(V)) and nitarsone (Nit(V)) have been used as animal growth enhancers and herbicides. Microbes contribute to redox cycling between the relatively less toxic pentavalent and highly toxic trivalent arsenicals. In this study, we report the identification of nemRA operon from Enterobacter sp. Z1 and show that it is involved in trivalent organoarsenical oxidation. Expression of nemA is induced by chromate (Cr(VI)), Rox(III), and Nit(III). Heterologous expression of NemA in Escherichia coli confers resistance to Cr(VI), methylarsenite (MAs(III)), Rox(III), and Nit(III). Purified NemA catalyzes simultaneous Cr(VI) reduction and MAs(III)/Rox(III)/Nit(III) oxidation, and oxidation was enhanced in the presence of Cr(VI). The results of electrophoretic mobility shift assays and fluorescence assays demonstrate that the transcriptional repressor, NemR, binds to either Rox(III) or Nit(III). NemR has three conserved cysteine residues, Cys21, Cys106, and Cys116. Mutation of any of the three resulted in loss of response to Rox(III)/Nit(III), indicating that they form an Rox(III)/Nit(III) binding site. These results show that NemA is a novel trivalent organoarsenical oxidase that is regulated by the trivalent organoarsenical-selective repressor NemR. This discovery expands our knowledge of the molecular mechanisms of organoarsenical oxidation and provides a basis for studying the redox coupling of environmental toxic compounds.
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Affiliation(s)
- Kaixiang Shi
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, P. R. China
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, Florida 33199, United States
| | - Manohar Radhakrishnan
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, Florida 33199, United States
| | - Xingli Dai
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, P. R. China
| | - Barry P Rosen
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, Florida 33199, United States
| | - Gejiao Wang
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, P. R. China
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10
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Bafana A, Khan F, Suguna K. Purification, characterization, and crystal structure of YhdA-type azoreductase from Bacillus velezensis. Proteins 2020; 89:483-492. [PMID: 33289153 DOI: 10.1002/prot.26032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2020] [Revised: 11/06/2020] [Accepted: 11/28/2020] [Indexed: 12/13/2022]
Abstract
Azoreductases are being extensively investigated for their ability to initiate degradation of recalcitrant azo dyes through reduction of azo bonds. There is great interest in studying their diversity, structure, and function to facilitate better understanding and effective application. Current study reports azoreductase enzyme from Bacillus velezensis, which showed 69.5% identity to the Bacillus subtilis azoreductase YhdA. The enzyme was homotetrameric and molecular weight of each subunit was 20 kDa. It decolorized azo dyes with different structures. The Vmax for decolorization of congo red, methyl orange and methyl red was 14.7, 28.6, and 77.9 nmol/min/mg, respectively. The enzyme contained FMN as cofactor and used NADPH as the favored co-substrate. It was oxygen-insensitive, but the presence of reducing agents enhanced its activity, which is a new finding. The azoreductase expression in B. velezensis was found to be unaffected by addition of azo dyes, although azo dyes are known to induce azoreductase expression in few organisms. The enzyme was thermostable with melting temperature of 89.5°C and functioned in wide temperature range. Further, the enzyme was crystallized and its structure was solved. The structural basis of its functional attributes is discussed. In our knowledge, this is the first report on characterization of azoreductase enzyme from B. velezensis.
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Affiliation(s)
- Amit Bafana
- Director's Research Cell, CSIR-NEERI (National Environmental Engineering Research Institute), Nagpur, India
| | - Farha Khan
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India.,David Geffen School of Medicine, Department of Physiology, University of California, Los Angeles, Los Angeles, USA
| | - Kaza Suguna
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
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11
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Han H, Zheng Y, Zhou T, Liu P, Li X. Cu(II) nonspecifically binding chromate reductase NfoR promotes Cr(VI) reduction. Environ Microbiol 2020; 23:415-430. [PMID: 33201569 DOI: 10.1111/1462-2920.15329] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 10/30/2020] [Accepted: 11/15/2020] [Indexed: 11/26/2022]
Abstract
Cu(II)-enhanced microbial Cr(VI) reduction is common in the environment, yet its mechanism is unknown. The specific activity of chromate reductase, NfoR, from Staphylococcus aureus sp. LZ-01 was augmented 1.5-fold by Cu(II). Isothermal titration calorimetry and spectral data show that Cu(II) binds to NfoR nonspecifically. Further, Cu(II) stimulates the nitrobenzene reduction of NfoR, indicating that Cu(II) promotes electron transfer. The crystal structure of NfoR in complex with CuSO4 (1.46 Å) was determined. The overall structure of NfoR-Cu(II) complex is a dimer that covalently binds with FMN and Cu(II)-binding pocket is located at the interface of the NfoR dimer. Structural superposition revealed that NfoR resembles the structure of class II chromate reductase. Site-directed mutagenesis revealed that Leu46 and Phe123 were involved in NADH binding, whereas Trp70 and Ser45 were the key residues for nitrobenzene binding. Furthermore, His100 and Asp171 were preferential affinity sites for Cu(II) and that Cys163 is an active site for FMN binding. Attenuation reductase activity in C163S can be partially restored to 54% wild type by increasing Cu(II) concentration. Partial restoration indicates dual-channel electron transfer of NfoR via Cu(II) and FMN. We propose a catalytic mechanism for Cu(II)-enhanced NfoR activity in which Cu(I) is formed transiently. Together, the current results provide an insight on Cu (II)-induced enhancement and benefit of Cr(VI) bioremediation.
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Affiliation(s)
- Huawen Han
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Science, Lanzhou University, Lanzhou, China
| | - Yuanzhang Zheng
- Department of Chemistry and Biochemistry, Loyola University Chicago, Chicago, IL, USA
| | - Tuoyu Zhou
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Science, Lanzhou University, Lanzhou, China
| | - Pu Liu
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Science, Lanzhou University, Lanzhou, China
| | - Xiangkai Li
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Science, Lanzhou University, Lanzhou, China
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Páez-Espino AD, Nikel PI, Chavarría M, de Lorenzo V. ArsH protects Pseudomonas putida from oxidative damage caused by exposure to arsenic. Environ Microbiol 2020; 22:2230-2242. [PMID: 32202357 DOI: 10.1111/1462-2920.14991] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 03/17/2020] [Accepted: 03/19/2020] [Indexed: 01/01/2023]
Abstract
The two As resistance arsRBC operons of Pseudomonas putida KT2440 are followed by a downstream gene called arsH that encodes an NADPH-dependent flavin mononucleotide reductase. In this work, we show that the arsH1 and (to a lesser extent) arsH2 genes of P. putida KT2440 strengthened its tolerance to both inorganic As(V) and As(III) and relieved the oxidative stress undergone by cells exposed to either oxyanion. Furthermore, overexpression of arsH1 and arsH2 endowed P. putida with a high tolerance to the oxidative stress caused by diamide (a drainer of metabolic NADPH) in the absence of any arsenic. To examine whether the activity of ArsH was linked to a direct action on the arsenic compounds tested, arsH1 and arsH2 genes were expressed in Escherichia coli, which has an endogenous arsRBC operon but lacks an arsH ortholog. The resulting clones both deployed a lower production of reactive oxygen species (ROS) when exposed to As salts and had a superior endurance to physiological redox insults. These results suggest that besides the claimed direct action on organoarsenicals, ArsH contributes to relieve toxicity of As species by mediating reduction of ROS produced in vivo upon exposure to the oxyanion, e.g. by generating FMNH2 to fuel ROS-quenching activities.
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Affiliation(s)
- A David Páez-Espino
- Systems Biology Department, Centro Nacional de Biotecnología (CNB-CSIC), Campus de Cantoblanco, Madrid, 28049, Spain
- Mammoth Biosciences Inc. South San Francisco, CA, 94080, USA
| | - Pablo I Nikel
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800, Kongens Lyngby, Denmark
| | - Max Chavarría
- Escuela de Química & CIPRONA, Universidad de Costa Rica, San José, 11501-2060, Costa Rica
| | - Víctor de Lorenzo
- Systems Biology Department, Centro Nacional de Biotecnología (CNB-CSIC), Campus de Cantoblanco, Madrid, 28049, Spain
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Pérez-Palacios P, Funes-Pinter I, Agostini E, Talano MA, Ibáñez SG, Humphry M, Edwards K, Rodríguez-Llorente ID, Caviedes MA, Pajuelo E. Targeting Acr3 from Ensifer medicae to the plasma membrane or to the tonoplast of tobacco hairy roots allows arsenic extrusion or improved accumulation. Effect of acr3 expression on the root transcriptome. Metallomics 2019; 11:1864-1886. [PMID: 31588944 DOI: 10.1039/c9mt00191c] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Transgenic tobacco hairy roots expressing the bacterial arsenite efflux pump Acr3 from Ensifer medicae were generated. The gene product was targeted either to the plasma membrane (ACR3 lines) or to the tonoplast by fusing the ACR3 protein to the tonoplast integral protein TIP1.1 (TIP-ACR3 lines). Roots expressing Acr3 at the tonoplast showed greater biomass than those expressing Acr3 at the plasma membrane. Furthermore, higher contents of malondialdehyde (MDA) and RNA degradation in ACR3 lines were indicative of higher oxidative stress. The determination of ROS-scavenging enzymes depicted the transient role of peroxidases in ROS detoxification, followed by the action of superoxide dismutase during both short- and medium-term exposure periods. Regarding As accumulation, ACR3 lines accumulated up to 20-30% less As, whereas TIP-ACR3 achieved a 2-fold increase in As accumulation in comparison to control hairy roots. Strategies that presumably induce As uptake, such as phosphate deprivation or dehydration followed by rehydration in the presence of As, fostered As accumulation up to 10 800 μg g-1. Finally, the effects of the heterologous expression of acr3 on the root transcriptome were assessed. Expression at the plasma membrane induced drastic changes in gene expression, with outstanding overexpression of genes related to electron transport, ATP synthesis and ATPases, suggesting that As efflux is the main detoxification mechanism in these lines. In addition, genes encoding heat shock proteins and those related to proline synthesis and drought tolerance were activated. On the other hand, TIP-ACR3 lines showed a similar gene expression profile to that of control roots, with overexpression of the glutathione and phytochelatin synthesis pathways, together with secondary metabolism pathways as the most important resistance mechanisms in TIP-ACR3, for which As allocation into the vacuole allowed better growth and stress management. Our results suggest that modulation of As accumulation can be achieved by subcellular targeting of Acr3: expression at the tonoplast enhances As accumulation in roots, whereas expression at the plasma membrane could promote As efflux. Thus, both approaches open the possibilities for developing safer crops when grown on As-polluted paddy soils, but expression at the tonoplast leads to better growth and less stressed roots, since the high energy cost of As efflux likely compromises growth in ACR3 lines.
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Affiliation(s)
- Patricia Pérez-Palacios
- Departamento de Microbiología y Parasitología, Facultad de Farmacia, Universidad de Sevilla, c/Profesor García González, 2, 41012-Sevilla, Spain. and Departamento de Biología Molecular, FCEFQyN, Universidad Nacional de Río Cuarto, Ruta Nacional 36 - Km. 601 - Río Cuarto, Córdoba, Argentina and Plant Biotechnology Division, British American Tobacco, Cambridge, CB4 0WA, UK
| | - Iván Funes-Pinter
- Departamento de Microbiología y Parasitología, Facultad de Farmacia, Universidad de Sevilla, c/Profesor García González, 2, 41012-Sevilla, Spain. and Facultad de Ciencias Agrarias, Universidad Nacional de Cuyo, Mendoza (CP 5507), Atte Brown 500, Chacras de Coria, Argentina
| | - Elizabeth Agostini
- Departamento de Biología Molecular, FCEFQyN, Universidad Nacional de Río Cuarto, Ruta Nacional 36 - Km. 601 - Río Cuarto, Córdoba, Argentina
| | - Melina A Talano
- Departamento de Biología Molecular, FCEFQyN, Universidad Nacional de Río Cuarto, Ruta Nacional 36 - Km. 601 - Río Cuarto, Córdoba, Argentina
| | - Sabrina G Ibáñez
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina
| | - Matt Humphry
- British American Tobacco (Investments) Ltd, Cambridge, CB4 0WA, UK
| | - Kieron Edwards
- Plant Biotechnology Division, British American Tobacco, Cambridge, CB4 0WA, UK
| | - Ignacio D Rodríguez-Llorente
- Departamento de Microbiología y Parasitología, Facultad de Farmacia, Universidad de Sevilla, c/Profesor García González, 2, 41012-Sevilla, Spain.
| | - Miguel A Caviedes
- Departamento de Microbiología y Parasitología, Facultad de Farmacia, Universidad de Sevilla, c/Profesor García González, 2, 41012-Sevilla, Spain.
| | - Eloísa Pajuelo
- Departamento de Microbiología y Parasitología, Facultad de Farmacia, Universidad de Sevilla, c/Profesor García González, 2, 41012-Sevilla, Spain.
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Suzuki H. Remarkable diversification of bacterial azoreductases: primary sequences, structures, substrates, physiological roles, and biotechnological applications. Appl Microbiol Biotechnol 2019; 103:3965-3978. [PMID: 30941462 DOI: 10.1007/s00253-019-09775-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 03/13/2019] [Accepted: 03/15/2019] [Indexed: 12/12/2022]
Abstract
Azoreductases reductively cleave azo linkages by using NAD(P)H as an electron donor. The enzymes are widely found in bacteria and act on numerous azo dyes, which allow various unique applications. This review describes primary amino acid sequences, structures, substrates, physiological roles, and biotechnological applications of bacterial azoreductases to discuss their remarkable diversification. According to primary sequences, azoreductases were classified phylogenetically into four main clades. Most members of clades I-III are flavoproteins, whereas clade IV members include flavin-free azoreductases. Clades I and II prefer NADPH and NADH, respectively, as electron donors, whereas other members generally use both. Several enzymes formed no clades; moreover, some bacteria produce azoreductases with longer primary structures than those hitherto identified, which implies further diversification of bacterial azoreductases. The crystal structures commonly reveal the Rossmann folds; however, ternary structures are moderately varied with different quaternary conformation. Although physiological roles are obscure, several azoreductases have been shown to act on metabolites such as flavins, quinones, and metal ions more efficiently than on azo dyes. Considering that many homologs exclusively act on these metabolites, it is possible that azoreductases are actually side activities of versatile reductases that act on various substrates with different specificities. In parallel, this idea raises the possibility that homologous enzymes, even if these are already defined as other types of reductases, widely harbor azoreductase activities. Although azoreductases for which their genes have been identified are not abundant, it may be simple to identify azoreductases of biotechnological importance that have novel substrate specificities.
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Affiliation(s)
- Hirokazu Suzuki
- Faculty of Engineering, Tottori University, 4-101 Koyama-Minami, Tottori, 680-8552, Japan. .,Center for Research on Green Sustainable Chemistry, Tottori University, 4-101 Koyama-Minami, Tottori, 680-8552, Japan.
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15
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Yan G, Chen X, Du S, Deng Z, Wang L, Chen S. Genetic mechanisms of arsenic detoxification and metabolism in bacteria. Curr Genet 2018; 65:329-338. [PMID: 30349994 DOI: 10.1007/s00294-018-0894-9] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 09/25/2018] [Accepted: 10/13/2018] [Indexed: 02/06/2023]
Abstract
Arsenic, distributed pervasively in the natural environment, is an extremely toxic substance which can severely impair the normal functions of living cells. Research on the genetic mechanisms of arsenic metabolism is of great importance for remediating arsenic-contaminated environments. Many organisms, including bacteria, have developed various strategies to tolerate arsenic, by either detoxifying this harmful element or utilizing it for energy generation. This review summarizes arsenic detoxification as well as arsenic respiratory metabolic pathways in bacteria and discusses novel arsenic resistance pathways in various bacterial strains. This knowledge provides insights into the mechanisms of arsenic biotransformation in bacteria. Multiple detoxification strategies among bacteria imply possible functional relationships among different arsenic detoxification/metabolism pathways. In addition, this review sheds light on the bioremediation of arsenic-contaminated environments and prevention of antibiotic resistance.
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Affiliation(s)
- Ge Yan
- Ministry of Education Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, School of Pharmaceutical Sciences, Zhongnan Hospital, Wuhan University, Wuhan, 430071, Hubei, China.,Taihe Hospital, Hubei University of Medicine, Shiyan, 442000, Hubei, China
| | - Xingxiang Chen
- Ministry of Education Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, School of Pharmaceutical Sciences, Zhongnan Hospital, Wuhan University, Wuhan, 430071, Hubei, China
| | - Shiming Du
- Taihe Hospital, Hubei University of Medicine, Shiyan, 442000, Hubei, China
| | - Zixin Deng
- Ministry of Education Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, School of Pharmaceutical Sciences, Zhongnan Hospital, Wuhan University, Wuhan, 430071, Hubei, China
| | - Lianrong Wang
- Ministry of Education Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, School of Pharmaceutical Sciences, Zhongnan Hospital, Wuhan University, Wuhan, 430071, Hubei, China
| | - Shi Chen
- Ministry of Education Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, School of Pharmaceutical Sciences, Zhongnan Hospital, Wuhan University, Wuhan, 430071, Hubei, China. .,Taihe Hospital, Hubei University of Medicine, Shiyan, 442000, Hubei, China.
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Abstract
Since the original report that Halomonas sp. strain GFAJ-1 was capable of using arsenic instead of phosphorus to sustain growth, additional studies have been conducted, and GFAJ-1 is now considered a highly arsenic-resistant but phosphorus-dependent bacterium. However, the mechanisms supporting the extreme arsenic resistance of the GFAJ-1 strain remain unknown. In this study, we show that GFAJ-1 has multiple distinct arsenic resistance mechanisms. It lacks the genes to reduce arsenate, which is the essential step in the well-characterized resistance mechanism of arsenate reduction coupled to arsenite extrusion. Instead, GFAJ-1 has two arsenic resistance operons, arsH1-acr3-2-arsH2 and mfs1-mfs2-gapdh, enabling tolerance to high levels of arsenate. mfs2 and gapdh encode proteins homologous to Pseudomonas aeruginosa ArsJ and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), respectively, which constitute the equivalent of an As(V) efflux system to catalyze the transformation of inorganic arsenate to pentavalent organoarsenical 1-arseno-3-phosphoglycerate and its subsequent extrusion. Surprisingly, the arsH1-acr3-2-arsH2 operon seems to consist of typical arsenite resistance genes, but this operon is sufficient to confer both arsenite and arsenate resistance on Escherichia coli AW3110 even in the absence of arsenate reductase, suggesting a novel pathway of arsenic detoxification. The simultaneous occurrence of these two unusual detoxification mechanisms enables the adaptation of strain GFAJ-1 to the particularly arsenic-rich environment of Mono Lake. Halomonas sp. strain GFAJ-1 was previously reported to use arsenic as a substitute for phosphorus to sustain life under phosphate-limited conditions. Although this claim was later undermined by several groups, how GFAJ-1 can thrive in environments with high arsenic concentrations remains unclear. Here, we determined that this ability can be attributed to the possession of two arsenic detoxification operons, arsH1-acr3-2-arsH2 and mfs1-mfs2-gapdh. mfs2 and gapdh encode proteins homologous to ArsJ and GAPDH in Pseudomonas aeruginosa; these proteins create an arsenate efflux pathway to reduce cellular arsenate accumulation. Interestingly, the combination of acr3-2 with either arsH gene was sufficient to confer resistance to both arsenite and arsenate in E. coli AW3110, even in the absence of arsenate reductase, suggesting a new strategy for bacterial arsenic detoxification. This study concludes that the survival of GFAJ-1 in high arsenic concentrations is attributable to the cooccurrence of these two unusual arsenic detoxification mechanisms.
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17
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Chang JS, Yoon IH, Kim KW. Arsenic biotransformation potential of microbial arsH responses in the biogeochemical cycling of arsenic-contaminated groundwater. CHEMOSPHERE 2018; 191:729-737. [PMID: 29080535 DOI: 10.1016/j.chemosphere.2017.10.044] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Revised: 10/05/2017] [Accepted: 10/07/2017] [Indexed: 06/07/2023]
Abstract
ArsH encodes an oxidoreductase, an NAD(P)H-dependent mononucleotide reductase, with an unknown function, frequently within an ars operon, and is widely distributed in bacteria. Novel arsenite-oxidizing bacteria have been isolated from arsenic-contaminated groundwater and surface soil in Vietnam. We found that ArsH gene activity, with arsenite oxidase in the periplasm; it revealed arsenic oxidation potential of the arsH system. Batch experiment results revealed Citrobacter freundii strain VTan4 (DQ481466) and Pseudomonas putida strain VTw33 (DQ481482) completely oxidized 1 mM of arsenite to arsenate within 30-50 h. High concentrations of arsenic were detected in groundwater and surrounding soil obtained from Vinh Tru village in Ha Nam province (groundwater: 11.0 μg/L to 37.0 μg/L; and soil: 2.5 mg/kg, 390.1 mg/kg), respectively. An arsH gene encoding an organoarsenical oxidase protein was observed in arsenite-oxidizing Citrobacter freundii strain VTan4 (DQ481466), whereas arsB, arsH, and arsH were detected in Pseudomonas putida strain VTw33 (DQ481482). arsH gene in bacteria was first reported from Vietnam for resistance and arsenite oxidase. We proposed that residues, Ser 43, Arg 45, Ser 48, and Tyr 49 are required for arsenic binding and activation of arsH. The ars-mediated biotransformation strongly influenced potential arsenite oxidase enzyme of the operon encoding a homogeneous arsH. Results suggest that the further study of arsenite-oxidizing bacteria may lead to a better understanding of arsenite oxidase responses, such as those of arsH, that may be applied to control biochemical properties; for example, speciation, detoxification, bioremediation, biotransformation, and mobilization of arsenic in contaminated groundwater.
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Affiliation(s)
- Jin-Soo Chang
- Molecular Biogeochemistry Laboratory, Biological & Genetic Resources Institute (BGRI), Hannam University (Jeonmin Campus), 505 Inno-Biz Park, 1646 Yuseong-daero, Yeseong-gu, Daejeon, 34054, Republic of Korea
| | - In-Ho Yoon
- Decommissioning Technology Research Division, Korea Atomic Energy Research Institute (KAERI), 111 Daedeok-daero, 989 Beon-gil, Yuseong-gu, Daejeon, 34057, Republic of Korea
| | - Kyoung-Woong Kim
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology (GIST), 261 Cheomdan-gwagiro, Buk-gu, Gwangju, 61005, Republic of Korea.
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18
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Li J, Pawitwar SS, Rosen BP. The organoarsenical biocycle and the primordial antibiotic methylarsenite. Metallomics 2017; 8:1047-1055. [PMID: 27730229 DOI: 10.1039/c6mt00168h] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Arsenic is the most pervasive environmental toxic substance. As a consequence of its ubiquity, nearly every organism has genes for resistance to inorganic arsenic. In bacteria these genes are found largely in bacterial arsenic resistance (ars) operons. Recently a parallel pathway for synthesis and degradation of methylated arsenicals has been identified. The arsM gene product encodes the ArsM (AS3MT in animals) As(iii) S-adenosylmethionine methyltransferase that methylates inorganic trivalent arsenite in three sequential steps to methylarsenite MAs(iii), dimethylarsenite (DMAs(iii) and trimethylarsenite (TMAs(iii)). MAs(iii) is considerably more toxic than As(iii), and we have proposed that MAs(iii) was a primordial antibiotic. Under aerobic conditions these products are oxidized to nontoxic pentavalent arsenicals, so that methylation became a detoxifying pathway after the atmosphere became oxidizing. Other microbes have acquired the ability to regenerate MAs(v) by reduction, transforming it again into toxic MAs(iii). Under this environmental pressure, MAs(iii) resistances evolved, including the arsI, arsH and arsP genes. ArsI is a C-As bond lyase that demethylates MAs(iii) back to less toxic As(iii). ArsH re-oxidizes MAs(iii) to MAs(v). ArsP actively extrudes MAs(iii) from cells. These proteins confer resistance to this primitive antibiotic. This oscillation between MAs(iii) synthesis and detoxification is an essential component of the arsenic biogeocycle.
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Affiliation(s)
- Jiaojiao Li
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, 11200 S.W. 8 Street, Miami, FL 33199 USA
| | - Shashank S Pawitwar
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, 11200 S.W. 8 Street, Miami, FL 33199 USA
| | - Barry P Rosen
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, 11200 S.W. 8 Street, Miami, FL 33199 USA
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Konjik V, Brünle S, Demmer U, Vanselow A, Sandhoff R, Ermler U, Mack M. Die Kristallstruktur von RosB: Einblicke in den Reaktionsmechanismus des ersten Mitglieds einer flavodoxinähnlichen Enzymfamilie. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201610292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Valentino Konjik
- Hochschule Mannheim; Paul-Wittsack-Straße 10 68163 Mannheim Deutschland
| | - Steffen Brünle
- Max-Planck-Institut für Biophysik; Max-von-Laue-Straße 3 60438 Frankfurt am Main Deutschland
| | - Ulrike Demmer
- Max-Planck-Institut für Biophysik; Max-von-Laue-Straße 3 60438 Frankfurt am Main Deutschland
| | - Amanda Vanselow
- Hochschule Mannheim; Paul-Wittsack-Straße 10 68163 Mannheim Deutschland
| | - Roger Sandhoff
- Deutsches Krebsforschungszentrum (DKFZ); Im Neuenheimer Feld 280 69120 Heidelberg Deutschland
| | - Ulrich Ermler
- Max-Planck-Institut für Biophysik; Max-von-Laue-Straße 3 60438 Frankfurt am Main Deutschland
| | - Matthias Mack
- Hochschule Mannheim; Paul-Wittsack-Straße 10 68163 Mannheim Deutschland
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Konjik V, Brünle S, Demmer U, Vanselow A, Sandhoff R, Ermler U, Mack M. The Crystal Structure of RosB: Insights into the Reaction Mechanism of the First Member of a Family of Flavodoxin-like Enzymes. Angew Chem Int Ed Engl 2016; 56:1146-1151. [DOI: 10.1002/anie.201610292] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Indexed: 11/06/2022]
Affiliation(s)
- Valentino Konjik
- Mannheim University of Applied Sciences; Paul-Wittsack-Strasse 10 68163 Mannheim Germany
| | - Steffen Brünle
- Max-Planck-Institute for Biophysics; Max-von-Laue-Strasse 3 60438 Frankfurt am Main Germany
| | - Ulrike Demmer
- Max-Planck-Institute for Biophysics; Max-von-Laue-Strasse 3 60438 Frankfurt am Main Germany
| | - Amanda Vanselow
- Mannheim University of Applied Sciences; Paul-Wittsack-Strasse 10 68163 Mannheim Germany
| | - Roger Sandhoff
- German Cancer Research Center (DKFZ); Im Neuenheimer Feld 280 69120 Heidelberg Germany
| | - Ulrich Ermler
- Max-Planck-Institute for Biophysics; Max-von-Laue-Strasse 3 60438 Frankfurt am Main Germany
| | - Matthias Mack
- Mannheim University of Applied Sciences; Paul-Wittsack-Strasse 10 68163 Mannheim Germany
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Resistance of Permafrost and Modern Acinetobacter lwoffii Strains to Heavy Metals and Arsenic Revealed by Genome Analysis. BIOMED RESEARCH INTERNATIONAL 2016; 2016:3970831. [PMID: 27795957 PMCID: PMC5067307 DOI: 10.1155/2016/3970831] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 07/14/2016] [Accepted: 09/07/2016] [Indexed: 12/23/2022]
Abstract
We performed whole-genome sequencing of five permafrost strains of Acinetobacter lwoffii (frozen for 15–3000 thousand years) and analyzed their resistance genes found in plasmids and chromosomes. Four strains contained multiple plasmids (8–12), which varied significantly in size (from 4,135 to 287,630 bp) and genetic structure; the fifth strain contained only two plasmids. All large plasmids and some medium-size and small plasmids contained genes encoding resistance to various heavy metals, including mercury, cobalt, zinc, cadmium, copper, chromium, and arsenic compounds. Most resistance genes found in the ancient strains of A. lwoffii had their closely related counterparts in modern clinical A. lwoffii strains that were also located on plasmids. The vast majority of the chromosomal resistance determinants did not possess complete sets of the resistance genes or contained truncated genes. Comparative analysis of various A. lwoffii and of A. baumannii strains discovered a number of differences between them: (i) chromosome sizes in A. baumannii exceeded those in A. lwoffii by about 20%; (ii) on the contrary, the number of plasmids in A. lwoffii and their total size were much higher than those in A. baumannii; (iii) heavy metal resistance genes in the environmental A. lwoffii strains surpassed those in A. baumannii strains in the number and diversity and were predominantly located on plasmids. Possible reasons for these differences are discussed.
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Nocelli N, Bogino PC, Banchio E, Giordano W. Roles of Extracellular Polysaccharides and Biofilm Formation in Heavy Metal Resistance of Rhizobia. MATERIALS 2016; 9:ma9060418. [PMID: 28773540 PMCID: PMC5456807 DOI: 10.3390/ma9060418] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Revised: 05/09/2016] [Accepted: 05/17/2016] [Indexed: 12/04/2022]
Abstract
Bacterial surface components and extracellular compounds, particularly flagella, lipopolysaccharides (LPSs), and exopolysaccharides (EPSs), in combination with environmental signals and quorum-sensing signals, play crucial roles in bacterial autoaggregation, biofilm development, survival, and host colonization. The nitrogen-fixing species Sinorhizobium meliloti (S. meliloti) produces two symbiosis-promoting EPSs: succinoglycan (or EPS I) and galactoglucan (or EPS II). Studies of the S.meliloti/alfalfa symbiosis model system have revealed numerous biological functions of EPSs, including host specificity, participation in early stages of host plant infection, signaling molecule during plant development, and (most importantly) protection from environmental stresses. We evaluated functions of EPSs in bacterial resistance to heavy metals and metalloids, which are known to affect various biological processes. Heavy metal resistance, biofilm production, and co-culture were tested in the context of previous studies by our group. A range of mercury (Hg II) and arsenic (As III) concentrations were applied to S. meliloti wild type strain and to mutant strains defective in EPS I and EPS II. The EPS production mutants were generally most sensitive to the metals. Our findings suggest that EPSs are necessary for the protection of bacteria from either Hg (II) or As (III) stress. Previous studies have described a pump in S. meliloti that causes efflux of arsenic from cells to surrounding culture medium, thereby protecting them from this type of chemical stress. The presence of heavy metals or metalloids in culture medium had no apparent effect on formation of biofilm, in contrast to previous reports that biofilm formation helps protect various microorganism species from adverse environmental conditions. In co-culture experiments, EPS-producing heavy metal resistant strains exerted a protective effect on AEPS-non-producing, heavy metal-sensitive strains; a phenomenon termed “rescuing” of the non-resistant strain.
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Affiliation(s)
- Natalia Nocelli
- Departamento de Biología Molecular, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Río Cuarto, Córdoba X5804BYA, Argentina.
| | - Pablo C Bogino
- Departamento de Biología Molecular, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Río Cuarto, Córdoba X5804BYA, Argentina.
| | - Erika Banchio
- Departamento de Biología Molecular, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Río Cuarto, Córdoba X5804BYA, Argentina.
| | - Walter Giordano
- Departamento de Biología Molecular, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Río Cuarto, Córdoba X5804BYA, Argentina.
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Abstract
Arsenic is the most pervasive environmental substance and is classified by the International Agency for Research on Cancer as a Group 1 human carcinogen. Nearly every organism has resistance pathways for inorganic arsenic, and in bacteria, their genes are found in arsenic resistance (ars) operons. Recently, a parallel pathway for organic arsenicals has been identified. The ars genes responsible for the organoarsenical detoxification includes arsM, which encodes an As(III) S-adenosylmethionine methyltransferase, arsI, which encodes a C–As bond lyase, and arsH, which encodes a methylarsenite oxidase. The identification and properties of arsM, arsI and arsH are described in this review.
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WrpA Is an Atypical Flavodoxin Family Protein under Regulatory Control of the Brucella abortus General Stress Response System. J Bacteriol 2016; 198:1281-93. [PMID: 26858101 DOI: 10.1128/jb.00982-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 01/27/2016] [Indexed: 12/13/2022] Open
Abstract
UNLABELLED The general stress response (GSR) system of the intracellular pathogen Brucella abortus controls the transcription of approximately 100 genes in response to a range of stress cues. The core genetic regulatory components of the GSR are required for B. abortus survival under nonoptimal growth conditions in vitro and for maintenance of chronic infection in an in vivo mouse model. The functions of the majority of the genes in the GSR transcriptional regulon remain undefined. bab1_1070 is among the most highly regulated genes in this regulon: its transcription is activated 20- to 30-fold by the GSR system under oxidative conditions in vitro. We have solved crystal structures of Bab1_1070 and demonstrate that it forms a homotetrameric complex that resembles those of WrbA-type NADH:quinone oxidoreductases, which are members of the flavodoxin protein family. However, B. abortus WrbA-related protein (WrpA) does not bind flavin cofactors with a high affinity and does not function as an NADH:quinone oxidoreductase in vitro. Soaking crystals with flavin mononucleotide (FMN) revealed a likely low-affinity binding site adjacent to the canonical WrbA flavin binding site. Deletion of wrpA (ΔwrpA) does not compromise cell survival under acute oxidative stress in vitro or attenuate infection in cell-based or mouse models. However, a ΔwrpA strain does elicit increased splenomegaly in a mouse model, suggesting that WrpA modulates B. abortus interaction with its mammalian host. Despite high structural homology with canonical WrbA proteins, we propose that B. abortus WrpA represents a functionally distinct member of the diverse flavodoxin family. IMPORTANCE Brucella abortus is an etiological agent of brucellosis, which is among the most common zoonotic diseases worldwide. The general stress response (GSR) regulatory system of B. abortus controls the transcription of approximately 100 genes and is required for maintenance of chronic infection in a murine model; the majority of GSR-regulated genes remain uncharacterized. We present in vitro and in vivo functional and structural analyses of WrpA, whose expression is strongly induced by GSR under oxidative conditions. Though WrpA is structurally related to NADH:quinone oxidoreductases, it does not bind redox cofactors in solution, nor does it exhibit oxidoreductase activity in vitro. However, WrpA does affect spleen inflammation in a murine infection model. Our data provide evidence that WrpA forms a new functional class of WrbA/flavodoxin family proteins.
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Identification of novel members of the bacterial azoreductase family in Pseudomonas aeruginosa. Biochem J 2015; 473:549-58. [PMID: 26621870 DOI: 10.1042/bj20150856] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 11/30/2015] [Indexed: 11/17/2022]
Abstract
Azoreductases are a family of diverse enzymes found in many pathogenic bacteria as well as distant homologues being present in eukarya. In addition to having azoreductase activity, these enzymes are also suggested to have NAD(P)H quinone oxidoreductase (NQO) activity which leads to a proposed role in plant pathogenesis. Azoreductases have also been suggested to play a role in the mammalian pathogenesis of Pseudomonas aeruginosa. In view of the importance of P. aeruginosa as a pathogen, we therefore characterized recombinant enzymes following expression of a group of putative azoreductase genes from P. aeruginosa expressed in Escherichia coli. The enzymes include members of the arsenic-resistance protein H (ArsH), tryptophan repressor-binding protein A (WrbA), modulator of drug activity B (MdaB) and YieF families. The ArsH, MdaB and YieF family members all show azoreductase and NQO activities. In contrast, WrbA is the first enzyme to show NQO activity but does not reduce any of the 11 azo compounds tested under a wide range of conditions. These studies will allow further investigation of the possible role of these enzymes in the pathogenesis of P. aeruginosa.
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Armendariz AL, Talano MA, Wevar Oller AL, Medina MI, Agostini E. Effect of arsenic on tolerance mechanisms of two plant growth-promoting bacteria used as biological inoculants. J Environ Sci (China) 2015; 33:203-210. [PMID: 26141894 DOI: 10.1016/j.jes.2014.12.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 12/26/2014] [Accepted: 12/29/2014] [Indexed: 06/04/2023]
Abstract
Bacterial ability to colonize the rhizosphere of plants in arsenic (As) contaminated soils is highly important for symbiotic and free-living plant growth-promoting rhizobacteria (PGPR) used as inoculants, since they can contribute to enhance plant As tolerance and limit metalloid uptake by plants. The aim of this work was to study the effect of As on growth, exopolysaccharide (EPS) production, biofilm formation and motility of two strains used as soybean inoculants, Bradyrhizobium japonicum E109 and Azospirillum brasilense Az39. The metabolism of arsenate (As(V)) and arsenite (As(III)) and their removal and/or possible accumulation were also evaluated. The behavior of both bacteria under As treatment was compared and discussed in relation to their potential for colonizing plant rhizosphere with high content of the metalloid. B. japonicum E109 growth was reduced with As(III) concentration from 10 μM while A. brasilense Az39 showed a reduction of growth with As(III) from 500 μM. EPS and biofilm production increased significantly under 25 μM As(III) for both strains. Moreover, this was more notorious for Azospirillum under 500 μM As(III), where motility was seriously affected. Both bacterial strains showed a similar ability to reduce As(V). However, Azospirillum was able to oxidize more As(III) (around 53%) than Bradyrhizobium (17%). In addition, both strains accumulated As in cell biomass. The behavior of Azospirillum under As treatments suggests that this strain would be able to colonize efficiently As contaminated soils. In this way, inoculation with A. brasilense Az39 would positively contribute to promoting growth of different plant species under As treatment.
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Affiliation(s)
- Ana L Armendariz
- Departamento de Biología Molecular, FCEFQyN, Universidad Nacional de Río Cuarto, CP 5800 Río Cuarto, Córdoba, Argentina.
| | - Melina A Talano
- Departamento de Biología Molecular, FCEFQyN, Universidad Nacional de Río Cuarto, CP 5800 Río Cuarto, Córdoba, Argentina
| | - Ana L Wevar Oller
- Departamento de Biología Molecular, FCEFQyN, Universidad Nacional de Río Cuarto, CP 5800 Río Cuarto, Córdoba, Argentina
| | - María I Medina
- Departamento de Biología Molecular, FCEFQyN, Universidad Nacional de Río Cuarto, CP 5800 Río Cuarto, Córdoba, Argentina
| | - Elizabeth Agostini
- Departamento de Biología Molecular, FCEFQyN, Universidad Nacional de Río Cuarto, CP 5800 Río Cuarto, Córdoba, Argentina
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Effects of Arsenite Resistance on the Growth and Functional Gene Expression of Leptospirillum ferriphilum and Acidithiobacillus thiooxidans in Pure Culture and Coculture. BIOMED RESEARCH INTERNATIONAL 2015; 2015:203197. [PMID: 26064886 PMCID: PMC4443643 DOI: 10.1155/2015/203197] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Revised: 03/16/2015] [Accepted: 03/18/2015] [Indexed: 11/18/2022]
Abstract
The response of iron-oxidizing Leptospirillum ferriphilum YSK and sulfur-oxidizing Acidithiobacillus thiooxidans A01 to arsenite under pure culture and coculture was investigated based on biochemical characterization (concentration of iron ion and pH value) and related gene expression. L. ferriphilum YSK and At. thiooxidans A01 in pure culture could adapt up to 400 mM and 800 mM As(III) after domestication, respectively, although arsenite showed a negative effect on both strains. The coculture showed a stronger sulfur and ferrous ion oxidation activity when exposed to arsenite. In coculture, the pH value showed no significant difference when under 500 mM arsenite stress, and the cell number of At. thiooxidans was higher than that in pure culture benefiting from the interaction with L. ferriphilum. The expression profile showed that the arsenic efflux system in the coculture was more active than that in pure culture, indicating that there is a synergetic interaction between At. thiooxidans A01 and L. ferriphilum YSK. In addition, a model was proposed to illustrate the interaction between arsenite and the ars operon in L. ferriphilum YSK and At. thiooxidans A01. This study will facilitate the effective application of coculture in the bioleaching process by taking advantage of strain-strain communication and coordination.
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Chen J, Bhattacharjee H, Rosen BP. ArsH is an organoarsenical oxidase that confers resistance to trivalent forms of the herbicide monosodium methylarsenate and the poultry growth promoter roxarsone. Mol Microbiol 2015; 96:1042-52. [PMID: 25732202 DOI: 10.1111/mmi.12988] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/01/2015] [Indexed: 11/29/2022]
Abstract
Environmental organoarsenicals are produced by microorganisms and are introduced anthropogenically as herbicides and antimicrobial growth promoters for poultry and swine. Nearly every prokaryote has an ars (arsenic resistance) operon, and some have an arsH gene encoding an atypical flavodoxin. The role of ArsH in arsenic resistance has been unclear. Here we demonstrate that ArsH is an organoarsenical oxidase that detoxifies trivalent methylated and aromatic arsenicals by oxidation to pentavalent species. Escherichia coli, which does not have an arsH gene, is very sensitive to the trivalent forms of the herbicide monosodium methylarsenate [MSMA or MAs(V)] and antimicrobial growth promoter roxarsone [Rox(V)], as well as to phenylarsenite [PhAs(III), also called phenylarsine oxide or PAO]. Pseudomonas putida has two chromosomally encoded arsH genes and is highly resistant to the trivalent forms of these organoarsenicals. A derivative of P. putida with both arsH genes deleted is sensitive to MAs(III), PhAs(III) or Rox(III). P. putida arsH expressed in E. coli conferred resistance to each trivalent organoarsenical. Cells expressing PpArsH oxidized the trivalent organoarsenicals. PpArsH was purified, and the enzyme in vitro similarly oxidized the trivalent organoarsenicals. These results suggest that ArsH catalyzes a novel biotransformation that confers resistance to environmental methylated and aromatic arsenicals.
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Affiliation(s)
- Jian Chen
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 33199, USA
| | - Hiranmoy Bhattacharjee
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 33199, USA
| | - Barry P Rosen
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 33199, USA
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Ajees AA, Rosen BP. As(III) S-adenosylmethionine methyltransferases and other arsenic binding proteins. GEOMICROBIOLOGY JOURNAL 2015; 32:570-576. [PMID: 26366023 PMCID: PMC4564252 DOI: 10.1080/01490451.2014.908983] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Efflux is by far the most common means of arsenic detoxification is by methylation catalyzed by a family of As(III) S-adenosylmethionine (SAM) methyltransferases (MTs) enzymes designated ArsM in microbes or AS3MT in higher eukaryotes. The protein sequence of more than 5000 AS3MT/ArsM orthologues have been deposited in the NCBI database, mostly in prokaryotic and eukaryotic microbes. As(III) SAM MTs are members of a large superfamily of MTs involved in numerous physiological functions. ArsMs detoxify arsenic by conversion of inorganic trivalent arsenic (As(III)) into mono-, di- and trimethylated species that may be more toxic and carcinogenic than inorganic arsenic. The pathway of methylation remains controversial. Several hypotheses will be examined in this review.
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Affiliation(s)
- A. Abdul Ajees
- Department of Atomic and Molecular Physics, LG-01, Academic Block -5, MIT Campus, Manipal University, Manipal – 576 104, Karnataka, India, Phone: +91-0820-2925072
| | - Barry P. Rosen
- Department of Cellular Biology and Pharmacology, Florida International University, Herbert Wertheim College of Medicine, Miami, Florida, USA 33199, 305-348-0657
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Xue XM, Yan Y, Xu HJ, Wang N, Zhang X, Ye J. ArsH fromSynechocystissp. PCC 6803 reduces chromate and ferric iron. FEMS Microbiol Lett 2014; 356:105-12. [DOI: 10.1111/1574-6968.12481] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Revised: 05/12/2014] [Accepted: 05/20/2014] [Indexed: 11/28/2022] Open
Affiliation(s)
- Xi-Mei Xue
- Key Laboratory of Urban Environment and Health; Institute of Urban Environment; Chinese Academy of Sciences; Xiamen China
- University of Chinese Academy of Sciences; Beijing China
| | - Yu Yan
- Key Laboratory of Urban Environment and Health; Institute of Urban Environment; Chinese Academy of Sciences; Xiamen China
- University of Chinese Academy of Sciences; Beijing China
| | - Hui-Juan Xu
- Key Laboratory of Urban Environment and Health; Institute of Urban Environment; Chinese Academy of Sciences; Xiamen China
- University of Chinese Academy of Sciences; Beijing China
| | - Ning Wang
- University of Chinese Academy of Sciences; Beijing China
- State Key Laboratory of Urban and Regional Ecology; Research Center for Eco-Environmental Sciences; Chinese Academy of Sciences; Beijing China
| | - Xiao Zhang
- Key Laboratory of Urban Environment and Health; Institute of Urban Environment; Chinese Academy of Sciences; Xiamen China
- University of Chinese Academy of Sciences; Beijing China
| | - Jun Ye
- Key Laboratory of Urban Environment and Health; Institute of Urban Environment; Chinese Academy of Sciences; Xiamen China
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Ryan A, Kaplan E, Nebel JC, Polycarpou E, Crescente V, Lowe E, Preston GM, Sim E. Identification of NAD(P)H quinone oxidoreductase activity in azoreductases from P. aeruginosa: azoreductases and NAD(P)H quinone oxidoreductases belong to the same FMN-dependent superfamily of enzymes. PLoS One 2014; 9:e98551. [PMID: 24915188 PMCID: PMC4051601 DOI: 10.1371/journal.pone.0098551] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 05/05/2014] [Indexed: 01/15/2023] Open
Abstract
Water soluble quinones are a group of cytotoxic anti-bacterial compounds that are secreted by many species of plants, invertebrates, fungi and bacteria. Studies in a number of species have shown the importance of quinones in response to pathogenic bacteria of the genus Pseudomonas. Two electron reduction is an important mechanism of quinone detoxification as it generates the less toxic quinol. In most organisms this reaction is carried out by a group of flavoenzymes known as NAD(P)H quinone oxidoreductases. Azoreductases have previously been separate from this group, however using azoreductases from Pseudomonas aeruginosa we show that they can rapidly reduce quinones. Azoreductases from the same organism are also shown to have distinct substrate specificity profiles allowing them to reduce a wide range of quinones. The azoreductase family is also shown to be more extensive than originally thought, due to the large sequence divergence amongst its members. As both NAD(P)H quinone oxidoreductases and azoreductases have related reaction mechanisms it is proposed that they form an enzyme superfamily. The ubiquitous and diverse nature of azoreductases alongside their broad substrate specificity, indicates they play a wide role in cellular survival under adverse conditions.
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Affiliation(s)
- Ali Ryan
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
- Faculty of Science, Engineering and Computing, Kingston University, Kingston upon Thames, United Kingdom
| | - Elise Kaplan
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Jean-Christophe Nebel
- Faculty of Science, Engineering and Computing, Kingston University, Kingston upon Thames, United Kingdom
| | - Elena Polycarpou
- Faculty of Science, Engineering and Computing, Kingston University, Kingston upon Thames, United Kingdom
| | - Vincenzo Crescente
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
- Faculty of Science, Engineering and Computing, Kingston University, Kingston upon Thames, United Kingdom
| | - Edward Lowe
- Laboratory of Molecular Biophysics, Biochemistry Department, University of Oxford, Oxford, United Kingdom
| | - Gail M. Preston
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
| | - Edith Sim
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
- Faculty of Science, Engineering and Computing, Kingston University, Kingston upon Thames, United Kingdom
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Kang YS, Shi Z, Bothner B, Wang G, McDermott TR. Involvement of the Acr3 and DctA anti-porters in arsenite oxidation in Agrobacterium tumefaciens 5A. Environ Microbiol 2014; 17:1950-62. [PMID: 24674103 DOI: 10.1111/1462-2920.12468] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Accepted: 03/22/2014] [Indexed: 12/01/2022]
Abstract
Microbial arsenite (AsIII) oxidation forms a critical piece of the arsenic cycle in nature, though our understanding of how and why microorganisms oxidize AsIII remains rudimentary. Our model organism Agrobacterium tumefaciens 5A contains two distinct ars operons (ars1 and ars2) that are similar in their coding region content. The ars1 operon is located nearby the aio operon that is essential for AsIII oxidation. The AsIII/H(+) anti-porters encoded by acr3-1 and acr3-2 are required for maximal AsIII and antimonite (SbIII) resistance, but acr3-1 (negatively regulated by ArsR-1) appears more active in this regard and also required for AsIII oxidation and expression of aioBA. A malate-phosphate anti-porter DctA is regulated by RpoN and AsIII, and is required for normal growth with malate as a sole carbon source. Qualitatively, a ΔdctA mutant was normal for AsIII oxidation and AsIII/SbIII resistance at metalloid concentrations inhibitory to the Δacr3-1 mutant; however, aioBA induction kinetics was significantly phase-shift delayed. Acr3 involvement in AsIII/SbIII resistance is reasonably well understood, but the role of Acr3 and DctA anti-porters in AsIII oxidation and its regulation is unexpected, and suggests that controlled AsIII trafficking across the cytoplasmic membrane is important to a process understood to occur in the periplasm.
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Affiliation(s)
- Yoon-Suk Kang
- Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, 59717, USA
| | - Zunji Shi
- Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, 59717, USA.,State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Brian Bothner
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT, 59717, USA
| | - Gejiao Wang
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Timothy R McDermott
- Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, 59717, USA
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Zhang X, Xue XM, Yan Y, Ye J. Purification, crystallization and preliminary X-ray diffraction analysis of ArsH from Synechocystis sp. strain PCC 6803. Acta Crystallogr F Struct Biol Commun 2014; 70:497-500. [PMID: 24699748 PMCID: PMC3976072 DOI: 10.1107/s2053230x14004865] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Accepted: 03/03/2014] [Indexed: 11/10/2022] Open
Abstract
ArsH is an NADPH-dependent flavin mononucleotide reductase and is frequently encoded as part of an ars operon. The function of the arsH gene remains to be characterized. Crystallization and structural studies may contribute to elucidating the specific biological function of ArsH associated with arsenic resistance. ArsH from Synechocystis sp. strain PCC 6803 was overproduced, purified and crystallized. Crystals were obtained by the sitting-drop vapour-diffusion method. Diffraction data were collected and processed to a resolution of 1.6 Å. The crystals belonged to the tetragonal space group I4122, with unit-cell parameters a = b = 127.94, c = 65.86 Å and one molecule in the asymmetric unit. Size-exclusion chromatography and molecular-replacement results showed that the ArsH formed a tetramer. Further structural analysis and comparison with ArsH from Sinorhizobium meliloti will provide information about the oligomerization of ArsH.
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Affiliation(s)
- Xiao Zhang
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, 1799 Jimei Road, Xiamen 361021, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
| | - Xi-Mei Xue
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, 1799 Jimei Road, Xiamen 361021, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
| | - Yu Yan
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, 1799 Jimei Road, Xiamen 361021, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
| | - Jun Ye
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, 1799 Jimei Road, Xiamen 361021, People’s Republic of China
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Identification of a novel membrane transporter mediating resistance to organic arsenic in Campylobacter jejuni. Antimicrob Agents Chemother 2014; 58:2021-9. [PMID: 24419344 DOI: 10.1128/aac.02137-13] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although bacterial mechanisms involved in the resistance to inorganic arsenic are well understood, the molecular basis for organic arsenic resistance has not been described. Campylobacter jejuni, a major food-borne pathogen causing gastroenteritis in humans, is highly prevalent in poultry and is reportedly resistant to the arsenic compound roxarsone (4-hydroxy-3-nitrobenzenearsonic acid), which has been used as a feed additive in the poultry industry for growth promotion. In this study, we report the identification of a novel membrane transporter (named ArsP) that contributes to organic arsenic resistance in Campylobacter. ArsP is predicted to be a membrane permease containing eight transmembrane helices, distinct from other known arsenic transporters. Analysis of multiple C. jejuni isolates from various animal species revealed that the presence of an intact arsP gene is associated with elevated resistance to roxarsone. In addition, inactivation of arsP in C. jejuni resulted in 4- and 8-fold reductions in the MICs of roxarsone and nitarsone, respectively, compared to that for the wild-type strain. Furthermore, cloning of arsP into a C. jejuni strain lacking a functional arsP gene led to 16- and 64-fold increases in the MICs of roxarsone and nitarsone, respectively. Neither mutation nor overexpression of arsP affected the MICs of inorganic arsenic, including arsenite and arsenate, in Campylobacter. Moreover, acquisition of arsP in NCTC 11168 led to accumulation of less roxarsone than the wild-type strain lacking arsP. Together, these results indicate that ArsP functions as an efflux transporter specific for extrusion of organic arsenic and contributes to the resistance to these compounds in C. jejuni.
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Shen Z, Han J, Wang Y, Sahin O, Zhang Q. The contribution of ArsB to arsenic resistance in Campylobacter jejuni. PLoS One 2013; 8:e58894. [PMID: 23554953 PMCID: PMC3598800 DOI: 10.1371/journal.pone.0058894] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Accepted: 02/07/2013] [Indexed: 11/21/2022] Open
Abstract
Arsenic, a toxic metalloid, exists in the natural environment and its organic form is approved for use as a feed additive for animal production. As a major foodborne pathogen of animal origin, Campylobacter is exposed to arsenic selection pressure in the food animal production environments. Previous studies showed that Campylobacter isolates from poultry were highly resistant to arsenic compounds and a 4-gene operon (containing arsP, arsR, arsC, and acr3) was associated with arsenic resistance in Campylobacter. However, this 4-gene operon is only present in some Campylobacter isolates and other arsenic resistance mechanisms in C. jejuni have not been characterized. In this study, we determined the role of several putative arsenic resistance genes including arsB, arsC2, and arsR3 in arsenic resistance in C. jejuni and found that arsB, but not the other two genes, contributes to the resistance to arsenite and arsenate. Inactivation of arsB in C. jejuni resulted in 8- and 4-fold reduction in the MICs of arsenite and arsenate, respectively, and complementation of the arsB mutant restored the MIC of arsenite. Additionally, overexpression of arsB in C. jejuni 11168 resulted in a 16-fold increase in the MIC of arsenite. PCR analysis of C. jejuni isolates from different animals hosts indicated that arsB and acr3 (the 4-gene operon) are widely distributed in various C. jejuni strains, suggesting that Campylobacter requires at least one of the two genes for adaptation to arsenic-containing environments. These results identify ArsB as an alternative mechanism for arsenic resistance in C. jejuni and provide new insights into the adaptive mechanisms of Campylobacter in animal food production environments.
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Affiliation(s)
- Zhangqi Shen
- Department of Veterinary Microbiology and Preventive Medicine, Iowa State University, Ames, Iowa, United States of America
| | - Jing Han
- Department of Veterinary Microbiology and Preventive Medicine, Iowa State University, Ames, Iowa, United States of America
| | - Yang Wang
- Department of Veterinary Microbiology and Preventive Medicine, Iowa State University, Ames, Iowa, United States of America
- Department of Pharmacology and Toxicology, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Orhan Sahin
- Department of Veterinary Microbiology and Preventive Medicine, Iowa State University, Ames, Iowa, United States of America
| | - Qijing Zhang
- Department of Veterinary Microbiology and Preventive Medicine, Iowa State University, Ames, Iowa, United States of America
- * E-mail:
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Duan J, Jiang W, Cheng Z, Heikkila JJ, Glick BR. The complete genome sequence of the plant growth-promoting bacterium Pseudomonas sp. UW4. PLoS One 2013; 8:e58640. [PMID: 23516524 PMCID: PMC3596284 DOI: 10.1371/journal.pone.0058640] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Accepted: 02/05/2013] [Indexed: 11/18/2022] Open
Abstract
The plant growth-promoting bacterium (PGPB) Pseudomonas sp. UW4, previously isolated from the rhizosphere of common reeds growing on the campus of the University of Waterloo, promotes plant growth in the presence of different environmental stresses, such as flooding, high concentrations of salt, cold, heavy metals, drought and phytopathogens. In this work, the genome sequence of UW4 was obtained by pyrosequencing and the gaps between the contigs were closed by directed PCR. The P. sp. UW4 genome contains a single circular chromosome that is 6,183,388 bp with a 60.05% G+C content. The bacterial genome contains 5,423 predicted protein-coding sequences that occupy 87.2% of the genome. Nineteen genomic islands (GIs) were predicted and thirty one complete putative insertion sequences were identified. Genes potentially involved in plant growth promotion such as indole-3-acetic acid (IAA) biosynthesis, trehalose production, siderophore production, acetoin synthesis, and phosphate solubilization were determined. Moreover, genes that contribute to the environmental fitness of UW4 were also observed including genes responsible for heavy metal resistance such as nickel, copper, cadmium, zinc, molybdate, cobalt, arsenate, and chromate. Whole-genome comparison with other completely sequenced Pseudomonas strains and phylogeny of four concatenated “housekeeping” genes (16S rRNA, gyrB, rpoB and rpoD) of 128 Pseudomonas strains revealed that UW4 belongs to the fluorescens group, jessenii subgroup.
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Affiliation(s)
- Jin Duan
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada.
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Devi PP, Adhikari S. Homology modeling and functional sites prediction of azoreductase enzyme from the cyanobacterium Nostoc sp. PCC7120. Interdiscip Sci 2013; 4:310-8. [DOI: 10.1007/s12539-012-0140-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2012] [Revised: 05/02/2012] [Accepted: 07/30/2012] [Indexed: 10/27/2022]
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Jin H, Zhang Y, Buchko GW, Varnum SM, Robinson H, Squier TC, Long PE. Structure determination and functional analysis of a chromate reductase from Gluconacetobacter hansenii. PLoS One 2012; 7:e42432. [PMID: 22879982 PMCID: PMC3412864 DOI: 10.1371/journal.pone.0042432] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Accepted: 07/09/2012] [Indexed: 11/19/2022] Open
Abstract
Environmental protection through biological mechanisms that aid in the reductive immobilization of toxic metals (e.g., chromate and uranyl) has been identified to involve specific NADH-dependent flavoproteins that promote cell viability. To understand the enzyme mechanisms responsible for metal reduction, the enzyme kinetics of a putative chromate reductase from Gluconacetobacter hansenii (Gh-ChrR) was measured and the crystal structure of the protein determined at 2.25 Å resolution. Gh-ChrR catalyzes the NADH-dependent reduction of chromate, ferricyanide, and uranyl anions under aerobic conditions. Kinetic measurements indicate that NADH acts as a substrate inhibitor; catalysis requires chromate binding prior to NADH association. The crystal structure of Gh-ChrR shows the protein is a homotetramer with one bound flavin mononucleotide (FMN) per subunit. A bound anion is visualized proximal to the FMN at the interface between adjacent subunits within a cationic pocket, which is positioned at an optimal distance for hydride transfer. Site-directed substitutions of residues proposed to involve in both NADH and metal anion binding (N85A or R101A) result in 90–95% reductions in enzyme efficiencies for NADH-dependent chromate reduction. In comparison site-directed substitution of a residue (S118A) participating in the coordination of FMN in the active site results in only modest (50%) reductions in catalytic efficiencies, consistent with the presence of a multitude of side chains that position the FMN in the active site. The proposed proximity relationships between metal anion binding site and enzyme cofactors is discussed in terms of rational design principles for the use of enzymes in chromate and uranyl bioremediation.
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Affiliation(s)
- Hongjun Jin
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America.
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Eswaramoorthy S, Poulain S, Hienerwadel R, Bremond N, Sylvester MD, Zhang YB, Berthomieu C, Van Der Lelie D, Matin A. Crystal structure of ChrR--a quinone reductase with the capacity to reduce chromate. PLoS One 2012; 7:e36017. [PMID: 22558308 PMCID: PMC3338774 DOI: 10.1371/journal.pone.0036017] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Accepted: 03/26/2012] [Indexed: 02/01/2023] Open
Abstract
The Escherichia coli ChrR enzyme is an obligatory two-electron quinone reductase that has many applications, such as in chromate bioremediation. Its crystal structure, solved at 2.2 Å resolution, shows that it belongs to the flavodoxin superfamily in which flavin mononucleotide (FMN) is firmly anchored to the protein. ChrR crystallized as a tetramer, and size exclusion chromatography showed that this is the oligomeric form that catalyzes chromate reduction. Within the tetramer, the dimers interact by a pair of two hydrogen bond networks, each involving Tyr128 and Glu146 of one dimer and Arg125 and Tyr85 of the other; the latter extends to one of the redox FMN cofactors. Changes in each of these amino acids enhanced chromate reductase activity of the enzyme, showing that this network is centrally involved in chromate reduction.
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Affiliation(s)
| | - Sébastien Poulain
- Department of Microbiology and Immunology, Stanford University, Stanford, California, United States of America
- CEA, DSV IBEB, Laboratoire des Interactions Protéine-Métal, Saint-Paul-lez-Durance, France
- CNRS, UMR Biologie Végétale et Microbiologie Environnementale, Saint-Paul-lez-Durance, France
- Université d'Aix-Marseille, Saint-Paul-lez-Durance, France
| | - Rainer Hienerwadel
- CNRS, UMR Biologie Végétale et Microbiologie Environnementale, Saint-Paul-lez-Durance, France
- Université d'Aix-Marseille, Laboratoire de Génétique et de Biophysique des Plantes, Marseille, France
- CEA, DSV IBEB, Marseille, France
| | - Nicolas Bremond
- CEA, DSV IBEB, Laboratoire des Interactions Protéine-Métal, Saint-Paul-lez-Durance, France
- CNRS, UMR Biologie Végétale et Microbiologie Environnementale, Saint-Paul-lez-Durance, France
- Université d'Aix-Marseille, Saint-Paul-lez-Durance, France
| | - Matthew D. Sylvester
- Department of Microbiology and Immunology, Stanford University, Stanford, California, United States of America
| | - Yian-Biao Zhang
- Department of Biology, Brookhaven National Laboratory, Upton, New York, United States of America
| | - Catherine Berthomieu
- CEA, DSV IBEB, Laboratoire des Interactions Protéine-Métal, Saint-Paul-lez-Durance, France
- CNRS, UMR Biologie Végétale et Microbiologie Environnementale, Saint-Paul-lez-Durance, France
- Université d'Aix-Marseille, Saint-Paul-lez-Durance, France
| | - Daniel Van Der Lelie
- Discovery and Analytical Sciences, RTI International, Research Triangle Park, North Carolina, United States of America
| | - A. Matin
- Department of Microbiology and Immunology, Stanford University, Stanford, California, United States of America
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Hervás M, López-Maury L, León P, Sánchez-Riego AM, Florencio FJ, Navarro JA. ArsH from the cyanobacterium Synechocystis sp. PCC 6803 is an efficient NADPH-dependent quinone reductase. Biochemistry 2012; 51:1178-87. [PMID: 22304305 DOI: 10.1021/bi201904p] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The cyanobacterium Synechocystis sp. PCC 6803 possesses an arsenic resistance operon that encodes, among others, an ArsH protein. ArsH is a flavin mononucleotide (FMN)-containing protein of unknown function and a member of the family of NADPH-dependent FMN reductases. The nature of its final electron acceptor and the role of ArsH in the resistance to arsenic remained to be clarified. Here we have expressed and purified Synechocystis ArsH and conducted an intensive biochemical study. We present kinetic evidence supporting a quinone reductase activity for ArsH, with a preference for quinones with hydrophobic substituents. By using steady-state activity measurements, as well as stopped-flow and laser-flash photolysis kinetic analyses, it has been possible to establish the mechanism of the process and estimate the values of the kinetic constants. Although the enzyme is able to stabilize the anionic semiquinone form of the FMN, reduction of quinones involves the hydroquinone form of the flavin cofactor, and the enzymatic reaction occurs through a ping-pong-type mechanism. ArsH is able to catalyze one-electron reactions (oxygen and cytocrome c reduction), involving the FMN semiquinone form, but with lower efficiency. In addition, arsH mutants are sensitive to the oxidizing agent menadione, suggesting that ArsH plays a role in the response to oxidative stress caused by arsenite.
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Affiliation(s)
- Manuel Hervás
- Instituto de Bioquímica Vegetal y Fotosíntesis, CSIC and Universidad de Sevilla, cicCartuja, Américo Vespucio 49, 41092 Seville, Spain
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Genome of halomonas strain GFAJ-1, a blueprint for fame or business as usual. J Bacteriol 2012; 194:1643-5. [PMID: 22267509 DOI: 10.1128/jb.00025-12] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Qin W, Huang Q, Zhu J, Yang P, Yu R, Li J, Liu X, Qiu G. Expression and function of two chaperone proteins, AtGroEL and AtGroES, from Acidithiobacillus ferrooxidans ATCC 23270. World J Microbiol Biotechnol 2011. [DOI: 10.1007/s11274-011-0781-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Ryan A, Wang CJ, Laurieri N, Westwood I, Sim E. Reaction mechanism of azoreductases suggests convergent evolution with quinone oxidoreductases. Protein Cell 2010; 1:780-90. [PMID: 21203919 DOI: 10.1007/s13238-010-0090-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Accepted: 06/28/2010] [Indexed: 01/17/2023] Open
Abstract
Azoreductases are involved in the bioremediation by bacteria of azo dyes found in waste water. In the gut flora, they activate azo pro-drugs, which are used for treatment of inflammatory bowel disease, releasing the active component 5-aminosalycilic acid. The bacterium P. aeruginosa has three azoreductase genes, paAzoR1, paAzoR2 and paAzoR3, which as recombinant enzymes have been shown to have different substrate specificities. The mechanism of azoreduction relies upon tautomerisation of the substrate to the hydrazone form. We report here the characterization of the P. aeruginosa azoreductase enzymes, including determining their thermostability, cofactor preference and kinetic constants against a range of their favoured substrates. The expression levels of these enzymes during growth of P. aeruginosa are altered by the presence of azo substrates. It is shown that enzymes that were originally described as azoreductases, are likely to act as NADH quinone oxidoreductases. The low sequence identities observed among NAD(P)H quinone oxidoreductase and azoreductase enzymes suggests convergent evolution.
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Affiliation(s)
- Ali Ryan
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford, OX1 3QT, UK
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Binter A, Staunig N, Jelesarov I, Lohner K, Palfey BA, Deller S, Gruber K, Macheroux P. A single intersubunit salt bridge affects oligomerization and catalytic activity in a bacterial quinone reductase. FEBS J 2009; 276:5263-74. [PMID: 19682074 DOI: 10.1111/j.1742-4658.2009.07222.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
YhdA, a thermostable NADPH:FMN oxidoreductase from Bacillus subtilis, reduces quinones via a ping-pong bi-bi mechanism with a pronounced preference for NADPH. The enzyme occurs as a stable tetramer in solution. The two extended dimer surfaces are packed against each other by a 90 rotation of one dimer with respect to the other. This assembly is stabilized by the formation of four salt bridges between K109 and D137 of the neighbouring protomers. To investigate the importance of the ion pair contacts, the K109L and D137L single replacement variants, as well as the K109L/D137L and K109D/D137K double replacement variants, were generated, expressed, purified, crystallized and biochemically characterized. The K109L and D137L variants form dimers instead of tetramers, whereas the K109L/D137L and K109D/D137K variants appear to exist in a dimer-tetramer equilibrium in solution. The crystal structures of the K109L and D137L variants confirm the dimeric state, with the K109L/D137L and K109D/D137K variants adopting a tetrameric assembly. Interestingly, all protein variants show a drastically reduced quinone reductase activity in steady-state kinetics. Detailed analysis of the two half reactions revealed that the oxidative half reaction is not affected, whereas reduction of the bound FMN cofactor by NADPH is virtually abolished. Inspection of the crystal structures indicates that the side chain of K109 plays a dual role by forming a salt bridge to D137, as well as stabilizing a glycine-rich loop in the vicinity of the FMN cofactor. In all protein variants, this glycine-rich loop exhibits a much higher mobility, compared to the wild-type. This appears to be incompatible with NADPH binding and thus leads to abrogation of flavin reduction.
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Affiliation(s)
- Alexandra Binter
- Institute of Biochemistry, Graz University of Technology, Austria
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Identification of an arsenic resistance and arsenic-sensing system in Campylobacter jejuni. Appl Environ Microbiol 2009; 75:5064-73. [PMID: 19502436 DOI: 10.1128/aem.00149-09] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Arsenic is commonly present in the natural environment and is also used as a feed additive for animal production. Poultry is a major reservoir for Campylobacter jejuni, a major food-borne human pathogen causing gastroenteritis. It has been shown that Campylobacter isolates from poultry are highly resistant to arsenic compounds, but the molecular mechanisms responsible for the resistance have not been determined, and it is unclear if the acquired arsenic resistance affects the susceptibility of Campylobacter spp. to other antimicrobials. In this study, we identified a four-gene operon that contributes to arsenic resistance in Campylobacter. This operon encodes a putative membrane permease (ArsP), a transcriptional repressor (ArsR), an arsenate reductase (ArsC), and an efflux protein (Acr3). PCR analysis of various clinical C. jejuni isolates indicated a significant association of this operon with elevated resistance to arsenite and arsenate. Gene-specific mutagenesis confirmed the role of the ars operon in conferring arsenic resistance. It was further shown that this operon is subject to regulation by ArsR, which directly binds to the ars promoter and inhibits the transcription of the operon. Arsenite inhibits the binding of ArsR to the ars promoter DNA and induces the expression of the ars genes. Mutation of the ars genes did not affect the susceptibility of C. jejuni to commonly used antibiotics. These results identify the ars operon as an important mechanism for arsenic resistance and sensing in Campylobacter.
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Páez-Espino D, Tamames J, de Lorenzo V, Cánovas D. Microbial responses to environmental arsenic. Biometals 2009; 22:117-30. [DOI: 10.1007/s10534-008-9195-y] [Citation(s) in RCA: 209] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2008] [Accepted: 12/07/2008] [Indexed: 10/21/2022]
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Branco R, Chung AP, Morais PV. Sequencing and expression of two arsenic resistance operons with different functions in the highly arsenic-resistant strain Ochrobactrum tritici SCII24T. BMC Microbiol 2008; 8:95. [PMID: 18554386 PMCID: PMC2440759 DOI: 10.1186/1471-2180-8-95] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2008] [Accepted: 06/13/2008] [Indexed: 11/16/2022] Open
Abstract
Background Arsenic (As) is a natural metalloid, widely used in anthropogenic activities, that can exist in different oxidation states. Throughout the world, there are several environments contaminated with high amounts of arsenic where many organisms can survive. The most stable arsenical species are arsenate and arsenite that can be subject to chemically and microbiologically oxidation, reduction and methylation reactions. Organisms surviving in arsenic contaminated environments can have a diversity of mechanisms to resist to the harmful effects of arsenical compounds. Results The highly metal resistant Ochrobactrum tritici SCII24 was able to grow in media with arsenite (50 mM), arsenate (up to 200 mM) and antimonite (10 mM). This strain contains two arsenic and antimony resistance operons (ars1 and ars2), which were cloned and sequenced. Sequence analysis indicated that ars1 operon contains five genes encoding the following proteins: ArsR, ArsD, ArsA, CBS-domain-containing protein and ArsB. The ars2 operon is composed of six genes that encode two other ArsR, two ArsC (belonging to different families of arsenate reductases), one ACR3 and one ArsH-like protein. The involvement of ars operons in arsenic resistance was confirmed by cloning both of them in an Escherichia coli ars-mutant. The ars1 operon conferred resistance to arsenite and antimonite on E. coli cells, whereas the ars2 operon was also responsible for resistance to arsenite and arsenate. Although arsH was not required for arsenate resistance, this gene seems to be important to confer high levels of arsenite resistance. None of ars1 genes were detected in the other type strains of genus Ochrobactrum, but sequences homologous with ars2 operon were identified in some strains. Conclusion A new strategy for bacterial arsenic resistance is described in this work. Two operons involved in arsenic resistance, one giving resistance to arsenite and antimonite and the other giving resistance to arsenate were found in the same bacterial strain.
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Affiliation(s)
- Rita Branco
- IMAR-Laboratory of Microbiology 3004-517 Coimbra, Portugal.
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