Intramolecular electron transfer in pseudomonas aeruginosa cd1 Nitrite reductase: Thermodynamics and kinetics
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Intramolecular electron transfer in pseudomonas aeruginosa cd1 Nitrite reductase : Thermodynamics and kinetics. / Farver, Ole; Brunori, Maurizio; Cutruzzolà, Francesca; Rinaldo, Serena; Wherland, Scot; Pecht, Israel.
In: Biophysical Journal, Vol. 96, No. 7, 2009, p. 2849-2856.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Intramolecular electron transfer in pseudomonas aeruginosa cd1 Nitrite reductase
T2 - Thermodynamics and kinetics
AU - Farver, Ole
AU - Brunori, Maurizio
AU - Cutruzzolà, Francesca
AU - Rinaldo, Serena
AU - Wherland, Scot
AU - Pecht, Israel
PY - 2009
Y1 - 2009
N2 - The cd(1) nitrite reductases, which catalyze the reduction of nitrite to nitric oxide, are homodimers of 60 kDa subunits, each containing one heme-c and one heme-d(1). Heme-c is the electron entry site, whereas heme-d(1) constitutes the catalytic center. The 3D structure of Pseudomonas aeruginosa nitrite reductase has been determined in both fully oxidized and reduced states. Intramolecular electron transfer (ET), between c and d(1) hemes is an essential step in the catalytic cycle. In earlier studies of the Pseudomonas stutzeri enzyme, we observed that a marked negative cooperativity is controlling this internal ET step. In this study we have investigated the internal ET in the wild-type and His369Ala mutant of P. aeruginosa nitrite reductases and have observed similar cooperativity to that of the Pseudomonas stutzeri enzyme. Heme-c was initially reduced, in an essentially diffusion-controlled bimolecular process, followed by unimolecular electron equilibration between the c and d(1) hemes (k(ET) = 4.3 s(-1) and K = 1.4 at 298 K, pH 7.0). In the case of the mutant, the latter ET rate was faster by almost one order of magnitude. Moreover, the internal ET rate dropped (by approximately 30-fold) as the level of reduction increased in both the WT and the His mutant. Equilibrium standard enthalpy and entropy changes and activation parameters of this ET process were determined. We concluded that negative cooperativity is a common feature among the cd(1) nitrite reductases, and we discuss this control based on the available 3D structure of the wild-type and the H369A mutant, in the reduced and oxidized states.
AB - The cd(1) nitrite reductases, which catalyze the reduction of nitrite to nitric oxide, are homodimers of 60 kDa subunits, each containing one heme-c and one heme-d(1). Heme-c is the electron entry site, whereas heme-d(1) constitutes the catalytic center. The 3D structure of Pseudomonas aeruginosa nitrite reductase has been determined in both fully oxidized and reduced states. Intramolecular electron transfer (ET), between c and d(1) hemes is an essential step in the catalytic cycle. In earlier studies of the Pseudomonas stutzeri enzyme, we observed that a marked negative cooperativity is controlling this internal ET step. In this study we have investigated the internal ET in the wild-type and His369Ala mutant of P. aeruginosa nitrite reductases and have observed similar cooperativity to that of the Pseudomonas stutzeri enzyme. Heme-c was initially reduced, in an essentially diffusion-controlled bimolecular process, followed by unimolecular electron equilibration between the c and d(1) hemes (k(ET) = 4.3 s(-1) and K = 1.4 at 298 K, pH 7.0). In the case of the mutant, the latter ET rate was faster by almost one order of magnitude. Moreover, the internal ET rate dropped (by approximately 30-fold) as the level of reduction increased in both the WT and the His mutant. Equilibrium standard enthalpy and entropy changes and activation parameters of this ET process were determined. We concluded that negative cooperativity is a common feature among the cd(1) nitrite reductases, and we discuss this control based on the available 3D structure of the wild-type and the H369A mutant, in the reduced and oxidized states.
KW - Cytochromes
KW - Electron Transport
KW - Heme
KW - Kinetics
KW - Mutation
KW - Nitrite Reductases
KW - Protein Conformation
KW - Pseudomonas aeruginosa
KW - Pulse Radiolysis
KW - Thermodynamics
U2 - 10.1016/j.bpj.2008.12.3937
DO - 10.1016/j.bpj.2008.12.3937
M3 - Journal article
C2 - 19348767
VL - 96
SP - 2849
EP - 2856
JO - Biophysical Journal
JF - Biophysical Journal
SN - 0006-3495
IS - 7
ER -
ID: 16331177