Definition of the Interaction Domain for Cytochrome con the Cytochrome bc 1 Complex

Tian, Hua; Sadoski, Robert C.; Zhang, Li; Yu, Linda; Durham, Bill; Millett, Francis

doi:10.1074/jbc.275.13.9587

Cited by 44 publications

(39 citation statements)

References 36 publications

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“…With a ⌬G ϭ 0 eV and a reasonable estimate of the reorganization energy of between 0.7 eV and 1 eV, an electron transfer rate of between 8.3 ϫ 10 6 s Ϫ1 and 9.7 ϫ 10 5 s Ϫ1 is calculated. This result compares to a measured transfer rate of 6 ϫ 10 4 s Ϫ1 for bovine QCR and horse heart CYC determined by using an artificially introduced electron donor, which affects CYC binding (32). This discrepancy suggests a significantly higher transfer rate in the natural environment than has been measured with the artificial donor.…”

Section: Resultsmentioning

confidence: 74%

Crystal structure of the yeast cytochrome bc ₁ complex with its bound substrate cytochrome c

Lange

Hunte

2002

Proc. Natl. Acad. Sci. U.S.A.

342

351

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Small diffusible redox proteins facilitate electron transfer in respiration and photosynthesis by alternately binding to integral membrane proteins. Specific and transient complexes need to be formed between the redox partners to ensure fast turnover. In respiration, the mobile electron carrier cytochrome c shuttles electrons from the cytochrome bc 1 complex to cytochrome c oxidase. Despite extensive studies of this fundamental step of energy metabolism, the structures of the respective electron transfer complexes were not known. Here we present the crystal structure of the complex between cytochrome c and the cytochrome bc 1 complex from Saccharomyces cerevisiae. The complex was crystallized with the help of an antibody fragment, and its structure was determined at 2.97-Å resolution. Cytochrome c is bound to subunit cytochrome c 1 of the enzyme. The tight and specific interactions critical for electron transfer are mediated mainly by nonpolar forces. The close spatial arrangement of the c-type hemes unexpectedly suggests a direct and rapid heme-to-heme electron transfer at a calculated rate of up to 8.3 ؋ 10 6 s ؊1 . Remarkably, cytochrome c binds to only one recognition site of the homodimeric multisubunit complex. Interestingly, the occupancy of quinone in the Qi site is higher in the monomer with bound cytochrome c, suggesting a coordinated binding and reduction of both electron-accepting substrates. Obviously, cytochrome c reduction by the cytochrome bc 1 complex can be regulated in response to respiratory conditions.

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Section: Resultsmentioning

confidence: 74%

Crystal structure of the yeast cytochrome bc ₁ complex with its bound substrate cytochrome c

Lange

Hunte

2002

Proc. Natl. Acad. Sci. U.S.A.

342

351

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“…Electrostatic forces are considered to be a dominant factor that contributes to binding of cytochrome c to cytochrome bc 1 , which is inferred from a significant salt dependence of electron transfer between these proteins (90,114,121,135,249). An importance of short-range hydrophobic interactions between surfaces of cytochrome c 1 subunit and cytochrome c was proposed on the basis of X-ray structures of cytochrome bc 1 co-crystallized with its redox partner (152,238).…”

Section: Cytochrome C Binding Sitementioning

confidence: 99%

“…Extensive chemical modifications and mutagenic studies identified crucial amino acid residues that stabilize the complex of the proteins through interactions of negatively and positively charged residues on the surfaces of cytochrome c 1 and c, respectively (30,163,241,249). The transient binding of cytochrome c to cytochrome bc 1 in solution was inferred from the analysis of electron transfer between these proteins (175) and from the measurements based on the techniques that were independent of electron transfer, such as plasmon wave-guide resonance spectroscopy (75) or EPR (206,221,224).…”

Section: Cytochrome C Binding Sitementioning

confidence: 99%

Electronic Connection Between the Quinone and CytochromecRedox Pools and Its Role in Regulation of Mitochondrial Electron Transport and Redox Signaling

Sarewicz

Osyczka

2015

Physiological Reviews

140

141

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Physiol Rev 95: 219 -243, 2015; doi:10.1152/physrev.00006.2014.-Mitochondrial respiration, an important bioenergetic process, relies on operation of four membranous enzymatic complexes linked functionally by mobile, freely diffusible elements: quinone molecules in the membrane and water-soluble cytochromes c in the intermembrane space. One of the mitochondrial complexes, complex III (cytochrome bc 1 or ubiquinol: cytochrome c oxidoreductase), provides an electronic connection between these two diffusible redox pools linking in a fully reversible manner two-electron quinone oxidation/reduction with one-electron cytochrome c reduction/oxidation. Several features of this homodimeric enzyme implicate that in addition to its well-defined function of contributing to generation of proton-motive force, cytochrome bc 1 may be a physiologically important point of regulation of electron flow acting as a sensor of the redox state of mitochondria that actively responds to changes in bioenergetic conditions. These features include the following: the opposing redox reactions at quinone catalytic sites located on the opposite sides of the membrane, the inter-monomer electronic connection that functionally links four quinone binding sites of a dimer into an H-shaped electron transfer system, as well as the potential to generate superoxide and release it to the intermembrane space where it can be engaged in redox signaling pathways. Here we highlight recent advances in understanding how cytochrome bc 1 may accomplish this regulatory physiological function, what is known and remains unknown about catalytic and side reactions within the quinone binding sites and electron transfers through the cofactor chains connecting those sites with the substrate redox pools. We also discuss the developed molecular mechanisms in the context of physiology of mitochondria.

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“…Very recently, the electric field generated by the reaction center in R. sphaeroides chromatophores was found to induce electron transfer from cyt b H to cyt b L with a half-time of 0.1 ms, establishing the rate constant for this important reaction (34). We have developed a ruthenium photoexcitation method to study intracomplex electron transfer of cyt c with cyt b 5 , cyt c peroxidase, cyt c oxidase, and cyt bc 1 (35)(36)(37)(38). The rate constant for intracomplex electron transfer between cyt c and cyt c 1 was determined to be 60,000 s Ϫ1 by this method (38).…”

mentioning

confidence: 99%

“…We have developed a ruthenium photoexcitation method to study intracomplex electron transfer of cyt c with cyt b 5 , cyt c peroxidase, cyt c oxidase, and cyt bc 1 (35)(36)(37)(38). The rate constant for intracomplex electron transfer between cyt c and cyt c 1 was determined to be 60,000 s Ϫ1 by this method (38). The development of a binuclear ruthenium complex to rapidly photooxidize cyt c 1 has allowed measurement of the rate constant for electron transfer from 2Fe-2S to cyt c 1 to be 80,000 s Ϫ1 in the R. sphaeroides cyt bc 1 complex (12).…”

mentioning

confidence: 99%

Photoinduced Electron Transfer between the Rieske Iron-Sulfur Protein and Cytochrome c1 in theRhodobacter sphaeroides Cytochromebc1 Complex

Engstrom¹,

Xiao²,

Yu³

et al. 2002

Journal of Biological Chemistry

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Electron transfer from the Rieske iron-sulfur protein to cytochrome c 1 (cyt c 1 ) in the Rhodobacter sphaeroides cytochrome bc 1 complex was studied using a ruthenium dimer complex, Ru 2 D. Laser flash photolysis of a solution containing reduced cyt bc 1 , Ru 2 D, and a sacrificial electron acceptor results in oxidation of cyt c 1 within 1 s, followed by electron transfer from the iron-sulfur center (2Fe-2S) to cyt c 1 with a rate constant of 80,000 s ؊1 . Experiments were carried out to evaluate whether the reaction was rate-limited by true electron transfer, proton gating, or conformational gating. The temperature dependence of the reaction yielded an enthalpy of activation of ؉17.6 kJ/mol, which is consistent with either rate-limiting conformational gating or electron transfer. The rate constant was nearly independent of pH over the range pH 7 to 9.5 where the redox potential of 2Fe-2S decreases significantly due to deprotonation of His-161. The rate constant was also not greatly affected by the Rieske iron-sulfur protein mutations Y156W, S154A, or S154A/Y156F, which decrease the redox potential of 2Fe-2S by 62, 109, and 159 mV, respectively. It is concluded that the electron transfer reaction from 2Fe-2S to cyt c 1 is controlled by conformational gating.The cytochrome bc 1 complex (ubiquinol:cytochrome c oxidoreductase) is an integral membrane protein in the energyconserving electron transport chains of mitochondria and many respiratory and photosynthetic prokaryotes (1). The complex contains the Rieske iron-sulfur protein, cyt 1 c 1 , and two b-type hemes (b L and b H ) in the cyt b subunit (1, 2). In the Q-cycle mechanism, the complex translocates four protons to the positive side of the membrane per two electrons transferred from ubiquinol to cyt c (2). In a key bifurcated reaction at the Q o site, the first electron is transferred from ubiquinol to the Rieske iron-sulfur center (2Fe-2S) and then to cyt c 1 and cyt c (1-3). The second electron is transferred from semiquinone in the Q o site to cyt b L and then to cyt b H and ubiquinone in the Q i site. Extensive x-ray crystallographic studies of cyt bc 1 have revealed that the Rieske iron-sulfur protein occurs in several different conformations depending on the crystal form and the presence of Q o site inhibitors ( Fig. 1) (4 -6). In native I4 1 22 bovine crystals an anomalous signal for 2Fe-2S is found close to cyt b L , but its intensity is small, suggesting that the Rieske iron-sulfur protein is conformationally mobile (4, 7). Addition of the Q o inhibitors UHDBT or stigmatellin significantly increased the intensity of 2Fe-2S, indicating that the Rieske iron-sulfur protein was immobilized with 2Fe-2S near the surface of cyt b L (7). In both chicken and yeast cyt bc 1 crystals, grown in the presence of stigmatellin, the Rieske iron-sulfur protein is in a conformation with 2Fe-2S proximal to the cyt b L heme, called the b state (5, 8). However, in native chicken or beef P6 5 22 crystals, the Rieske iron-sulfur protein is in a conformation with 2Fe-2S cl...

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Definition of the Interaction Domain for Cytochrome con the Cytochrome bc 1 Complex

Cited by 44 publications

References 36 publications

Crystal structure of the yeast cytochrome bc ₁ complex with its bound substrate cytochrome c

Crystal structure of the yeast cytochrome bc ₁ complex with its bound substrate cytochrome c

Electronic Connection Between the Quinone and CytochromecRedox Pools and Its Role in Regulation of Mitochondrial Electron Transport and Redox Signaling

Photoinduced Electron Transfer between the Rieske Iron-Sulfur Protein and Cytochrome c1 in theRhodobacter sphaeroides Cytochromebc1 Complex

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Definition of the Interaction Domain for Cytochrome con the Cytochrome bc 1 Complex

Cited by 44 publications

References 36 publications

Crystal structure of the yeast cytochrome bc 1 complex with its bound substrate cytochrome c

Crystal structure of the yeast cytochrome bc 1 complex with its bound substrate cytochrome c

Electronic Connection Between the Quinone and CytochromecRedox Pools and Its Role in Regulation of Mitochondrial Electron Transport and Redox Signaling

Photoinduced Electron Transfer between the Rieske Iron-Sulfur Protein and Cytochrome c1 in theRhodobacter sphaeroides Cytochromebc1 Complex

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Crystal structure of the yeast cytochrome bc ₁ complex with its bound substrate cytochrome c

Crystal structure of the yeast cytochrome bc ₁ complex with its bound substrate cytochrome c