Mössbauer studies of cytochrome c-551

Dwivedi, Arpit; Toscano, William A.; Debrunner, Peter G.

doi:10.1016/0005-2795(79)90425-2

Cited by 19 publications

(5 citation statements)

References 12 publications

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“…In the case of type II centers, g z is somewhat smaller, corresponding to a smaller A zz (40-66 T), and ∆E Q is larger (2.1-2.4 mm/s) than for type I. The parameters observed in our study for cytochromes b and f are very similar to those reported for type I centers, while those found for cytochrome c (54), where the methionine dominates the ligand effects, are close to type II parameters.…”

Section: Discussionsupporting

confidence: 85%

Mössbauer and Electron Paramagnetic Resonance Studies of the Cytochrome bf Complex

et al. 1999

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The (57)Fe-enriched cytochrome bf complex has been isolated from hydrocultures of spinach. It has been studied at different redox states by optical, EPR, and Mössbauer spectroscopy. The Mössbauer spectrum of the native complex at 190 K with all iron centers in the oxidized state reveals the presence of four different iron sites: low-spin ferric iron in cytochrome b [with an isomer shift (delta) of 0.20 mm/s, a quadrupole splitting (DeltaE(Q)) of 1.77 mm/s, and a relative area of 40%], low-spin ferric iron of cytochrome f (delta = 0.26 mm/s, DeltaE(Q) = 1.90 mm/s, and a relative area of 20%), and two high-spin ferric iron sites of the Rieske iron-sulfur protein (ISP) with a bis-cysteine and a bis-histidine ligated iron (delta(1) = 0.15 mm/s, DeltaE(Q1) = 0.70 mm/s, and a relative area of 20%, and delta(2) = 0.25 mm/s, DeltaE(Q2) = 0.90 mm/s, and a relative area of 20%, respectively). EPR and magnetic Mössbauer measurements at low temperatures corroborate these results. A crystal-field analysis of the EPR data and of the magnetic Mössbauer data yields estimates for the g-tensors (g(z)(), g(y)(), and g(x)()) of cytochrome b (3.60, 1.35, and 1.1) and of cytochrome f (3.51, 1.69, and 0.9). Addition of ascorbate reduces not only the iron of cytochrome f to the ferrous low-spin state (delta = 0.43 mm/s, DeltaE(Q) = 1.12 mm/s at 4.2 K) but also the bis-histidine coordinated iron of the Rieske 2Fe-2S center to the ferrous high-spin state (delta(2) = 0.73 mm/s, DeltaE(Q2) = -2.95 mm/s at 4.2 K). At this redox step, the Mössbauer parameters of cytochrome b have not changed, indicating that the redox changes of cytochrome f and the Rieske protein did not change the first ligand sphere of the low-spin ferric iron in cytochrome b. Reduction with dithionite further reduces the two hemes of cytochrome b to the ferrous low-spin state (delta = 0.49 mm/s, DeltaE(Q) = 1.08 mm/s at 4.2 K). The spin Hamiltonian analysis of the magnetic Mössbauer spectra at 4.2 K yields hyperfine parameters of the reduced Rieske 2Fe-2S center in the cytochrome bf complex which are very similar to those reported for the Rieske center from Thermus thermophilus [Fee, J. A., Findling, K. L., Yoshida, T., et al. (1984) J. Biol. Chem. 259, 124-133].

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Section: Discussionsupporting

confidence: 85%

Mössbauer and Electron Paramagnetic Resonance Studies of the Cytochrome bf Complex

et al. 1999

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“…The question arises as to the reason for the different relaxation behaviors of the complexes in this study. Ferriheme centers in proteins, such as the low-spin form of cytochrome P450 cam , several electron-transfer cytochromes, , the cytochrome b 6 f complex, and the histamine complexes of nitrophorins 2 and 4, , as well as 57 Fe-labeled ferriheme models in frozen solution, including [(TPP)Fe(NH 2 PzH) 2 ]Cl 71 and perp -[(OMTPP)Fe(1-MeIm) 2 ]Cl in this study, exhibit magnetically split Mössbauer spectra at 4.2 K in small applied fields. This indicates that the intrinsic relaxation rate, ω, of the electron spin of most of these centers is slower than the Larmor frequency, about 10 7 s -1 .…”

Section: Resultsmentioning

confidence: 65%

Section: Resultsmentioning

confidence: 99%

“…Mössbauer spectroscopy is another technique that has been utilized to characterize some ferriheme protein systems, ,− but no investigations of the mitochondrial Complexes II, III and IV have yet been reported. The magnetic Mössbauer spectra of several multi-heme protein complexes have been reported, ,, although it is very difficult to deconvolute the overlapping Mössbauer spectra of multi-heme complexes when the parameters of the centers are similar.…”

Section: Introductionmentioning

confidence: 99%

“…38,61 Reduction potentials for the b L and b H centers of murine Complex III are -31 ( 12 and +92 ( 14 mV, respectively, 62 and those for other mammalian b heme centers are similar, but all are affected by the conditions used for measurements, including detergent or lipid and the electron-transfer mediators used, as well as the presence of inhibitors that bind to the quinone sites and the state of oxidation of the quinone near heme b H . 63 Mo ¨ssbauer spectroscopy is another technique that has been utilized to characterize some ferriheme protein systems, 41,[64][65][66][67][68][69][70] but no investigations of the mitochondrial Complexes II, III and IV have yet been reported. The magnetic Mo ¨ssbauer spectra of several multi-heme protein complexes have been reported, 41,68,70 although it is very difficult to deconvolute the overlapping Mo ¨ssbauer spectra of multi-heme complexes when the parameters of the centers are similar.…”

Section: Introductionmentioning

confidence: 99%

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Models of the Membrane-Bound Cytochromes: Mössbauer Spectra of Crystalline Low-Spin Ferriheme Complexes Having Axial Ligand Plane Dihedral Angles Ranging from 0° to 90°

et al. 2006

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Crystalline samples of four low-spin Fe(III) octaalkyltetraphenylporphyrinate and two low-spin Fe (III) tetramesitylporphyrinate complexes, all of which are models of the bis-histidine-coordinated cytochromes of mitochondrial complexes II, III and IV, and chloroplast complex b 6 f, and whose molecular structures and EPR spectra have been reported previously, have been investigated in detail by Mössbauer spectroscopy. Of these, the first three have been shown to exhibit normal rhombic EPR spectra with three clearly-resolved g-values, while the last three have been shown to exhibit "large g max " EPR spectra at 4.2 K. It is found that the hyperfine coupling constants of the complexes are consistent with those reported previously for low-spin ferriheme systems, with the largest-magnitude hyperfine coupling constant, A zz , being considerably smaller for the "parallel" complexes (400-540 kG) than for the strictly perpendicular complex (902 kG), A xx being negative for all six complexes, and A zz and A xx being of similar magnitude for the "parallel" complexes (for example, for [(TMP)Fe(1-MeIm) 2 ]Cl, A zz = 400 kG, A xx = -400 kG), and finally, A yy is small, but difficult to estimate with accuracy for all complexes. With results for six structurally-characterized model systems we find qualitative correlations of g zz , A zz , and △E Q with axial ligand plane dihedral angle △φ.

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