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dc.contributor.authorGlasser, Nathaniel R.en
dc.contributor.authorOyala, Paul H.en
dc.contributor.authorOsborne, Thomas H.en
dc.contributor.authorSantini, Joanne M.en
dc.contributor.authorNewman, Dianne K.en
dc.date.accessioned2019-09-13T09:08:28Z
dc.date.available2019-09-13T09:08:28Z
dc.date.issued2018-08-13
dc.identifier.citationGlasser NR, Oyala PH, Osborne TH, Santini JM, Newman DK (2018) 'Structural and mechanistic analysis of the arsenate respiratory reductase provides insight into environmental arsenic transformations', Proceedings of the National Academy of Sciences, 115 (37), pp.E8614-E8623.en
dc.identifier.issn0027-8424
dc.identifier.pmid30104376
dc.identifier.doi10.1073/pnas.1807984115
dc.identifier.urihttp://hdl.handle.net/10547/623432
dc.description.abstractArsenate respiration by bacteria was discovered over two decades ago and is catalyzed by diverse organisms using the well-conserved Arr enzyme complex. Until now, the mechanisms underpinning this metabolism have been relatively opaque. Here, we report the structure of an Arr complex (solved by X-ray crystallography to 1.6-Å resolution), which was enabled by an improved Arr expression method in the genetically tractable arsenate respirer Shewanella sp. ANA-3. We also obtained structures bound with the substrate arsenate (1.8 Å), the product arsenite (1.8 Å), and the natural inhibitor phosphate (1.7 Å). The structures reveal a conserved active-site motif that distinguishes Arr [(R/K)GRY] from the closely related arsenite respiratory oxidase (Arx) complex (XGRGWG). Arr activity assays using methyl viologen as the electron donor and arsenate as the electron acceptor display two-site ping-pong kinetics. A Mo(V) species was detected with EPR spectroscopy, which is typical for proteins with a pyranopterin guanine dinucleotide cofactor. Arr is an extraordinarily fast enzyme that approaches the diffusion limit (Km = 44.6 ± 1.6 μM, kcat = 9,810 ± 220 seconds-1), and phosphate is a competitive inhibitor of arsenate reduction (Ki = 325 ± 12 μM). These observations, combined with knowledge of typical sedimentary arsenate and phosphate concentrations and known rates of arsenate desorption from minerals in the presence of phosphate, suggest that (i) arsenate desorption limits microbiologically induced arsenate reductive mobilization and (ii) phosphate enhances arsenic mobility by stimulating arsenate desorption rather than by inhibiting it at the enzymatic level.
dc.language.isoenen
dc.publisherNational Academy of Sciencesen
dc.relation.urlhttps://www.pnas.org/content/115/37/E8614.shorten
dc.relation.urlhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC6140538/en
dc.rightsYellow - can archive pre-print (ie pre-refereeing)
dc.subjectArrABen
dc.subjectbacterial arsenate respirationen
dc.subjectbiogeochemistryen
dc.subjectenzymologyen
dc.subjectF850 Environmental Sciencesen
dc.titleStructural and mechanistic analysis of the arsenate respiratory reductase provides insight into environmental arsenic transformationsen
dc.typeArticleen
dc.identifier.journalProceedings of the National Academy of Sciencesen
dc.identifier.pmcidPMC6140538
dc.date.updated2019-09-13T08:59:19Z
html.description.abstractArsenate respiration by bacteria was discovered over two decades ago and is catalyzed by diverse organisms using the well-conserved Arr enzyme complex. Until now, the mechanisms underpinning this metabolism have been relatively opaque. Here, we report the structure of an Arr complex (solved by X-ray crystallography to 1.6-Å resolution), which was enabled by an improved Arr expression method in the genetically tractable arsenate respirer Shewanella sp. ANA-3. We also obtained structures bound with the substrate arsenate (1.8 Å), the product arsenite (1.8 Å), and the natural inhibitor phosphate (1.7 Å). The structures reveal a conserved active-site motif that distinguishes Arr [(R/K)GRY] from the closely related arsenite respiratory oxidase (Arx) complex (XGRGWG). Arr activity assays using methyl viologen as the electron donor and arsenate as the electron acceptor display two-site ping-pong kinetics. A Mo(V) species was detected with EPR spectroscopy, which is typical for proteins with a pyranopterin guanine dinucleotide cofactor. Arr is an extraordinarily fast enzyme that approaches the diffusion limit (Km = 44.6 ± 1.6 μM, kcat = 9,810 ± 220 seconds-1), and phosphate is a competitive inhibitor of arsenate reduction (Ki = 325 ± 12 μM). These observations, combined with knowledge of typical sedimentary arsenate and phosphate concentrations and known rates of arsenate desorption from minerals in the presence of phosphate, suggest that (i) arsenate desorption limits microbiologically induced arsenate reductive mobilization and (ii) phosphate enhances arsenic mobility by stimulating arsenate desorption rather than by inhibiting it at the enzymatic level.


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