Alkali-induced reduction of the b-cytochromes in purified Complex III from beef heart mitochondria

Nelson, Bruce R.; Gellerfors, Pär

doi:10.1016/0005-2728(75)90034-1

Cited by 4 publications

(3 citation statements)

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“…The functional properties of the artificial Cb are closely related to the redox potentials of the two hemes. The redox potentials of the two hemes from the artificial Cb adopt values of −106 and −170 meV, which are relatively distant from −220 meV, the value of the redox potential of histidine/imidazole coordinated hemes in aqueous solution. , In contrast to these values, the measurements of the corresponding redox potentials of hemes in the native Cb subunit from the Cbc 1 protein complex adopt still more positive values, +93 and −34 meV. − Accordingly, the difference in the redox potentials between the high- and low-potential hemes is much larger for the native Cb subunit (127 meV) than for the artificial Cb (70 meV). Although the native and the artificial Cb contain the same cofactors, hemes axially ligated by histidines, the redox potentials of the hemes vary considerably due to differences in the protein environment.…”

Section: Introductionmentioning

confidence: 95%

“…33,34 In contrast to these values, the measurements of the corresponding redox potentials of hemes in the native Cb subunit from the Cbc 1 protein complex adopt still more positive values, +93 and -34 meV. [35][36][37] Accordingly, the difference in the redox potentials between the high-and low-potential hemes is much larger for the native Cb subunit (127 meV) than for the artificial Cb (70 meV). Although the native and the artificial Cb contain the same cofactors, hemes axially ligated by histidines, the redox potentials of the hemes vary considerably due to differences in the protein environment.…”

Section: Introductionmentioning

confidence: 98%

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Artificial Cytochrome b: Computer Modeling and Evaluation of Redox Potentials

et al. 2001

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We generated atomic coordinates of an artificial protein that was recently synthesized to model the central part of the native cytochrome b (Cb) subunit consisting of a four-helix bundle with two hemes. Since no X-ray structure is available, the structural elements of the artificial Cb were assembled from scratch using all known chemical and structural information available and avoiding strain as much as possible. Molecular dynamics (MD) simulations applied to this model protein exhibited root-mean-square deviations as small as those obtained from MD simulations starting with the crystal structure of the native Cb subunit. This demonstrates that the modeled structure of the artificial Cb is relatively rigid and strain-free. The model structure of the artificial Cb was used to determine the redox potentials of the two hemes by calculating the electrostatic energies from the solution of the linearized Poisson-Boltzmann equation (LPBE). The calculated redox potentials agree within 20 meV with the experimentally measured values. The dependence of the redox potentials of the hemes on the protein environment was analyzed. Accordingly, the total shift in the redox potentials is mainly due to the low dielectric medium of the protein, the protein backbone charges, and the salt bridges formed between the arginines and the propionic acid groups of the hemes. The difference in the shift of the redox potentials is due to the interactions with the hydrophilic side chains and the salt bridges formed with the propionic acids of the hemes. For comparison and to test the computational procedure, the redox potentials of the two hemes in the native Cb from the cytochrome bc(1) (Cbc(1)) complex were also calculated. Also in this case the computed redox potentials agree well with experiments.

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Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 98%

Artificial Cytochrome b: Computer Modeling and Evaluation of Redox Potentials

et al. 2001

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“…The effect of the ApH (pH gradient) on duroquinolcytochrome c reductase activity has not yet been successfully determined due: (i) To the lack of reliable methods for measuring internal pH in liposomal systems where the proton movement is directed outwards. (ii) To the fact that isolated duroquinol-cytochrome creductase is strongly pH dependent [3 ] , making acid-base transition experiments [ 131 difficult to interpret. It should be mentioned, however, that in several experiments we have observed valinomycin-activated rates to be 20-40% lower than FCCP-activated rates.…”

Section: Discussionmentioning

confidence: 99%