Stoichiometry of electron uptake and the effect of anions and pH on the molybdenum and heme reduction potentials of sulfite oxidase

Spence, J. T.; Kipke, Cary A.; Enemark, John H.; Sunde, Roger A.

doi:10.1021/ic00015a014

Cited by 48 publications

(68 citation statements)

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“…1a and b. The spectral features of reduced and oxidized SOx are practically identical to the spectra reported previously for spectral titration with mediators [15,16] and basically reflect the optical absorption properties of the heme. However, extra features can be followed from the obtained spectra at À 0.7 V. In addition to absorbance of the heme moiety, an absorbance change occurs within 300 -400 nm wavelengths, which could be presumably ascribed to the redox transformations of the Mo domain [2].…”

Section: Resultssupporting

confidence: 81%

“…(1) with the parameters: the number of electrons n equal to 0.98 F 0.05, the formal potential À 115 mV. These values correlate well with previously reported potentials for redox transformations of the heme domain of SOx [15,16]. Additionally, the absence of a histeresis of the titration curve might designate that it is the heme domain that is in the direct ET contact with the electrode surface; that is, no other redox centre acts as a mediator between the heme and the electrode.…”

Section: Resultssupporting

confidence: 81%

See 1 more Smart Citation

Spectroelectrochemical study of heme- and molybdopterin cofactor-containing chicken liver sulphite oxidase

Ferapontova

Christenson

Hellmark

et al. 2004

Bioelectrochemistry

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Section: Resultssupporting

confidence: 81%

Section: Resultssupporting

confidence: 81%

Spectroelectrochemical study of heme- and molybdopterin cofactor-containing chicken liver sulphite oxidase

Ferapontova

Christenson

Hellmark

et al. 2004

Bioelectrochemistry

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“…It is likely that the oxidation first occurs at the metal center in 1 as the peak potential for the oxidation is closer to the reversible Mo(V)/(VI) potentials seen for Mo(V)-oxotetra(alkyl-substituted benzenethiolate) complexes than any oxidation in the CV of the disulfide form or disodium salt of L (Conry RR, Erkizia E, Tipton AA, unpublished results; [97]). The potentials for the relevant molybdoenzymes vary tremendously from enzyme to enzyme and are very sensitive to the experimental conditions [100,101,102,103], making meaningful comparisons to the small-molecule systems difficult.…”

Section: Resultsmentioning

confidence: 99%

A mononuclear molybdenum(V) mono-oxo biphenyl-2,2′-dithiolate complex in which the metal resides within a cleft formed by the ligands and that exhibits N-H...S hydrogen bonding in the solid state

Conry

Tipton

2001

J. Biol. Inorg. Chem.

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The reaction of Mo(O)2(acac)2, H2L (2,2'-dimercaptobiphenyl), and NEt3 produced the mononuclear Mo(V) complex Et3NH[Mo(O)(L)2] (1). Molybdenum mono-oxo tetrathiolate complexes such as 1 are studied as potential structural or functional models for pyranopterin-containing molybdoenzymes. Complex 1 has been crystallographically characterized. The solid-state structure reveals that the molybdenum ion sits within a cleft formed by the biphenyl backbone of the ligands, providing some steric protection. In addition, there is a hydrogen bond between the amine hydrogen of [Et3NH]+ and one of the thiolate sulfur atoms. A difference in solution reactivity between 1 and a derivative without a hydrogen-bonding counterion suggests that hydrogen bonding occurs in solution also. There are two short S-S contacts and small S-Mo-S angles in the structure of 1 that may reflect a slight bonding interaction. Such short S-S distances and small angles have been found in a couple of other Mo-thiolate complexes and in many of the molybdoenzyme crystal structures. Further characterization of 1 by EPR, IR, and UV-vis spectroscopies, as well as by cyclic voltammetry, is discussed and compared to known Mo(V)-oxo-tetrathiolate complexes as well as to relevant molybdoenzyme data. Reactions to generate Mo(VI) complexes from 1 resulted in net oxidation at the ligand to form its disulfide derivative, which dissociated from the metal center. This result suggests that modifications to the ligand to prevent this process are needed.

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“…In chicken SUOX, the E m values have been reported to be Ϫ86 mV and 131 mV for the Mo(IV/V) and Mo(V/VI) couples, respectively (86), and in S. novella, they are reported to be Ϫ46 mV and 160 mV (42). Thus, a partial consensus suggests that the true SUOXs have widely separated E m values that render the Mo(V) electron paramagnetic resonance spectrum readily observable.…”

Section: Protein-ppt Interactionsmentioning

confidence: 99%

Evolutionary Persistence of the Molybdopyranopterin-Containing Sulfite Oxidase Protein Fold

Workun

Moquin

Rothery

et al. 2008

Microbiol Mol Biol Rev

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SUMMARY The importance of molybdoenzymes is exemplified both by the debilitating and fatal human diseases caused by their deficiency and by their persistence throughout evolution. Here, we show that the protein fold of the molybdopyranopterin-containing domain of sulfite oxidase (the SUOX fold) can be found in all three domains of life. Analyses of sequence data and protein structure comparisons (secondary structure matching) show that the SUOX fold is found in enzymes that have quite distinct macromolecular architectures comprising one or more domains and sometimes subsidiary subunits. These are summarized as follows: (i) animal SUOXs that contain an N-terminal cytochrome b 5 domain and an SUOX fold fused to a C-terminal dimerization domain; (ii) plant SUOX that contains an SUOX fold fused to a C-terminal dimerization domain; (iii) the YedY protein from Escherichia coli, which comprises only the SUOX fold; (iv) the sulfite dehydrogenase from Starkeya novella that contains the SUOX fold, a dimerization domain, and an additional c-type cytochrome subunit; and (v) the plant-type nitrate reductases, exemplified by that of Pichia angusta, that contain an N-terminal SUOX fold, a dimerization domain, a cytochrome b 5 domain, and a C-terminal NADH binding flavin adenine dinucleotide-containing domain. We used the primary sequences of the proteins containing an SUOX fold to mine 559 sequences of related proteins. A phylogeny of a nonredundant subset of these sequences was generated, and the resultant clades were categorized by sequence motif analyses in the context of the available protein structures. Based on the motif analyses, cladistics, and domain conservations, we are able to postulate a plausible pathway of SUOX fold enzyme evolution.

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Stoichiometry of electron uptake and the effect of anions and pH on the molybdenum and heme reduction potentials of sulfite oxidase

Cited by 48 publications

References 0 publications

Spectroelectrochemical study of heme- and molybdopterin cofactor-containing chicken liver sulphite oxidase

Spectroelectrochemical study of heme- and molybdopterin cofactor-containing chicken liver sulphite oxidase

A mononuclear molybdenum(V) mono-oxo biphenyl-2,2′-dithiolate complex in which the metal resides within a cleft formed by the ligands and that exhibits N-H...S hydrogen bonding in the solid state

Evolutionary Persistence of the Molybdopyranopterin-Containing Sulfite Oxidase Protein Fold

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