Pulse Radiolysis Studies on Nitrite Reductase from Achromobacter cycloclastes IAM 1013: Evidence for Intramolecular Electron Transfer from Type 1 Cu to Type 2 Cu

Suzuki, Shinnichiro; Kohzuma, Takamitsu; Deligeer,; Yamaguchi, Kazuya; Nakamura, Nobuhumi; Shidara, Sohsuke; Kobayashi, Kazuo; Tagawa, Seiichi

doi:10.1021/ja00103a035

Cited by 88 publications

(100 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In agreement with the earlier observations of Suzuki et al for the reactivity of AcNiR, AxgNiR and AxnNiR [12,13], a direct bimolecular reduction of the T1 Cu(II) site by NMNA 3 radicals was observed with a second order rate constant of k PWV = (5 þ 1)U10 V M 3I s 3I . We found this rate to be the same, within experimental error, when gy 3 2 radicals were used as the electron donor.…”

Section: Resultssupporting

confidence: 92%

“…A similar observation was made in the earlier pulse radiolysis studies [7,12,13]. Since the midpoint potential of T1 Cu(II)/Cu(I) for AxNiR has been reported to be 240 mV at 298 K [12] one may calculate a midpoint potential of T2 Cu(II)/Cu(I) from the above ET equilibrium to be 230 mV. This means that no driving force is available for the ET, in fact the T1-T2 ET is an`uphill' process.…”

Section: Resultssupporting

confidence: 85%

“…being a T2 Cu(II) centre, makes NiR an interesting system for studying intramolecular ET. Indeed, the T1 Cu(I) to T2 Cu(II) ET in NiRs isolated from three di¡erent bacteria has recently been observed [12,13]. This called for characterisation of the internal ET process in terms of the activation barriers for this reaction in NiR, to enable comparison with the analogous process taking place in AO.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The intramolecular electron transfer between copper sites of nitrite reductase: a comparison with ascorbate oxidase

et al. 1998

View full text Add to dashboard Cite

The intramolecular electron transfer (ET) between the type 1 Cu(I) and the type 2 Cu(II) sites of Alcaligenes xylosoxidans dissimilatory nitrite reductase (AxNiR) has been studied in order to compare it with the analogous process taking place in ascorbate oxidase (AO). This internal process is induced following reduction of the type 1 Cu(II) by radicals produced by pulse radiolysis. The reversible ET reaction proceeds with a rate constant k i = k I3P +k P3I of 450 þ 30 s 3I at pH 7.0 and 298 K. The equilibrium constant K was determined to be 0.7 at 298 K from which the individual rate constants for the forward and backward reactions were calculated to be: k I3P = 185 þ 12 s 3I and k P3I 265 þ 18 s 3I . The temperature dependence of K allowed us to determine the v vH³ value of the ET equilibrium to be 12.1 kJ mol 3I . Measurements of the temperature dependence of the ET process yielded the following activation parameters: forward reaction, v vH g = 22.7 þ 3.4 kJ mol 3I and v vS g = 3126 þ 11 J K 3I mol 3I ; backward reaction, v vH g = 10.6 þ 1.7 kJ mol 3I and v vS g = 3164 þ 15 J K 3I mol 3I . X-ray crystallographic studies of NiRs suggest that the most probable ET pathway linking the two copper sites consists of Cys IQT , which provides the thiolate ligand to the type 1 copper ion, and the adjacent His IQS residue with its imidazole being one of the ligands to the type 2 Cu ion. This pathway is essentially identical to that operating between the type 1 Cu(I) and the trinuclear copper centre in ascorbate oxidase, and the characteristics of the internal ET processes of these enzymes are compared. The data are consistent with the faster ET observed in nitrite reductase arising from a more advantageous entropy of activation when compared with ascorbate oxidase.z 1998 Federation of European Biochemical Societies.

show abstract

Section: Resultssupporting

confidence: 92%

Section: Resultssupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The intramolecular electron transfer between copper sites of nitrite reductase: a comparison with ascorbate oxidase

et al. 1998

View full text Add to dashboard Cite

show abstract

“…Such spectra show a decreasing, negative signal at 1237 cm Ϫ1 flanked by two exchanging bands at 1247 and 1224 cm Ϫ1 (isosbestic point at 1232 cm Ϫ1 ), resulting from the sulfonate moiety in the HEPES or MES buffer. To positively identify nitrite specific signals, the experiment was repeated using 15 N-labeled nitrite as a ligand. In this case, the intensity at 1237 cm Ϫ1 remained nearly constant, but a new signal decreasing with pH was observed at 1209 cm Ϫ1 (Fig.…”

Section: Methodsmentioning

confidence: 99%

“…After an electron is passed to the type 1 copper site from the electron donor protein, the electron is transferred on to nitrite via the type 2 copper ion (15). Although schematics of the enzymatic reaction typically only mention the species NO 2 Ϫ , it has * This work was supported by Swedish Natural Science Research Council and Stint.…”

mentioning

confidence: 99%

pH Dependence of Copper Geometry, Reduction Potential, and Nitrite Affinity in Nitrite Reductase

Jacobson

Pistorius

Farkas

et al. 2007

Journal of Biological Chemistry

View full text Add to dashboard Cite

Many properties of copper-containing nitrite reductase are pH-dependent, such as gene expression, enzyme activity, and substrate affinity. Here we use x-ray diffraction to investigate the structural basis for the pH dependence of activity and nitrite affinity by examining the type 2 copper site and its immediate surroundings in nitrite reductase from Rhodobacter sphaeroides 2.4.3. At active pH the geometry of the substrate-free oxidized type 2 copper site shows a near perfect tetrahedral geometry as defined by the positions of its ligands. At higher pH values the most favorable copper site geometry is altered toward a more distorted tetrahedral geometry whereby the solvent ligand adopts a position opposite to that of the His-131 ligand. This pH-dependent variation in type 2 copper site geometry is discussed in light of recent computational results. When co-crystallized with substrate, nitrite is seen to bind in a bidentate fashion with its two oxygen atoms ligating the type 2 copper, overlapping with the positions occupied by the solvent ligand in the high and low pH structures. Fourier transformation infrared spectroscopy is used to assign the pH dependence of the binding of nitrite to the active site, and EPR spectroscopy is used to characterize the pH dependence of the reduction potential of the type 2 copper site. Taken together, these spectroscopic and structural observations help to explain the pH dependence of nitrite reductase, highlighting the subtle relationship between copper site geometry, nitrite affinity, and enzyme activity.

show abstract

Interdomain electron transfer in flavohaemoglobin from Candida norvegensis with antibiotic azole compounds

2022

Self Cite

View full text Add to dashboard Cite

Flavohaemoglobins (FlavoHbs) function as nitric oxide dioxygenases, oxidizing nitric oxide with nitrite and shuttling electrons from NAD(P)H via FAD and O 2 . Here, using pulse radiolysis, we investigate intramolecular electron transfer between FAD and haem b in FlavoHbs. We found that reduction of FlavoHb with hydrated electrons proceeded via two phases: an initial fast phase and a second slower process. Absorbance measured at 600 nm revealed fast flavin reduction followed by a slower decrease corresponding to reoxidation of FAD. The slower process was partially lost in FlavoHbs lacking FAD. These results suggest that the slower phase is attributable to intramolecular electron transfer from FAD to the haem iron. The rate constant in the absence of azole compound (3.3 × 10 3 s -1 ) was accelerated ~10fold (2.7 × 10 4 s -1 ) by the binding of econazole, reflecting a conformational change in the open-to-closed transition.

show abstract

Pulse Radiolysis Studies on Nitrite Reductase from Achromobacter cycloclastes IAM 1013: Evidence for Intramolecular Electron Transfer from Type 1 Cu to Type 2 Cu

Cited by 88 publications

References 0 publications

The intramolecular electron transfer between copper sites of nitrite reductase: a comparison with ascorbate oxidase

The intramolecular electron transfer between copper sites of nitrite reductase: a comparison with ascorbate oxidase

pH Dependence of Copper Geometry, Reduction Potential, and Nitrite Affinity in Nitrite Reductase

Interdomain electron transfer in flavohaemoglobin from Candida norvegensis with antibiotic azole compounds

Contact Info

Product

Resources

About