Orientation of the haems of the ubiquinol oxidase: O2 reductase, cytochrome bo of Escherichia coli

Salerno, John C.; Ingledew, W. John

doi:10.1111/j.1432-1033.1991.tb16082.x

Cited by 14 publications

(8 citation statements)

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“…In the topology model (Figure 1), residues Hisl3, His70, and Hisl55 are located close to the cytoplasmic side of the membrane, whereas residues His28 and Hisll3 are closer to the outer side of the membrane. This arrangement indicates that His28 and His 113 could be the axial ligands to one heme and two of residues His 13, His70, and His 155 could be the axial ligands to the other heme, assuming a perpendicular orientation of the heme planes relative to the membrane plane, as is the case in other integral membranebound cytochromes b (Bergstrom, 1985;Salerno & Ingledew, 1991;Ingledew et al, 1992). For the single-heme anchor Cyt £>558, function as axial heme ligands (Yu et al, 1992;Daignan-Fomier et al, 1994).…”

Section: Discussionmentioning

confidence: 86%

Transmembrane topology and axial ligands to hemes in the cytochrome b subunit of Bacillus subtilis succinate:menaquinone reductase

et al. 1995

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The membrane-anchoring subunit of Bacillus subtilis succinate:menaquinone reductase is a protein of 202 residues containing two protoheme IX groups with bis-histidine axial ligation. Residues His13, His28, His70, His113, and His155 are the possible heme ligands. The transmembrane topology of this cytochrome was analyzed using fusions to alkaline phosphatase. The results support a proposed model with five transmembrane polypeptide segments and the N-terminus exposed to the cytoplasm. Mutant B. subtilis cytochromes containing a His13-->Tyr, a His28-->Tyr, and a His113-->Tyr mutation, respectively, were produced in Escherichia coli, partially purified, and analyzed. In addition, succinate: menaquinone reductase containing the His13-->Tyr mutation in the anchor subunit was overproduced in B. subtilis, purified, and characterized. The data demonstrate that His13 is not an axial heme ligand. Thermodynamic and spectroscopic properties of the cytochrome are, however, affected by the His13-->Tyr mutation; compared to wild type, the redox potentials of both hemes are negatively shifted and the gmax signal in the EPR spectrum of the high-potential heme is shifted from 3.68 to 3.50. From the combined results we conclude that His28 and His113 function as axial ligands to the low-potential heme, which is located in the membrane near the outer surface of the cytoplasmic membrane. Residues His70 and His155 ligate the high-potential heme, which is positioned close to His13 in the protein, near the inner surface of the membrane.

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Section: Discussionmentioning

confidence: 86%

Transmembrane topology and axial ligands to hemes in the cytochrome b subunit of Bacillus subtilis succinate:menaquinone reductase

et al. 1995

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“…The low-spin haem b558 is oriented with its plane perpendicular to the plane of the membrane. This is the orientation of haem b562 and the haem b556 of the mitochondrial cytochrome bel complex, of haem a and a3 of mitochondrial cytochrome aa,, of the chloroplast cytochrome b559 (Blum et al, 1978a,b), and of the two haem groups of cytochrome o from E. coli (Salerno & Ingledew, 1991). The orientation is one that may be expected of a haem group suspended between transmembrane sections of ac-helix, and it is possible that the haem is located between two such helices in the bilayer-spanning region of the complex.…”

Section: Discussionmentioning

confidence: 99%

The orientation of the three haems of the ‘in situ’ ubiquinol oxidase, cytochrome bd, of Escherichia coli

Ingledew

Rothery

Gennis

et al. 1992

Biochemical Journal

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The Escherichia coli cytochrome bd complex incorporates three haems as prosthetic groups. In the ferric form these are a predominantly high-spin chlorin (haem d), a high-spin haem b (b595) and a low-spin haem b (b558). The orientations of these three haems have been determined by e.p.r. studies on oriented multilayer preparations of cytoplasmic membrane fragments. The low-spin haem b (b558) and the high-spin haem d are oriented with their haem planes perpendicular to the membrane plane. The high-spin haem b595 is oriented with its haem plane at approx. 55 degrees to the membrane plane. A minor low-spin component, attributable to a low-spin subpopulation of the haem d, is also oriented with its haem plane perpendicular to the membrane plane.

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“…Mitochondria (heavy mitochondrial fraction) were prepared from ox heart muscle (Green and Ziegler, 1963) and were disrupted by a single passage through a French pressure cell as described previously (Salerno and Ingledew, 1991).…”

Section: Preparation Of Mitochondrial Membranesmentioning

confidence: 99%

“…Heme a lies with its normal in the membrane plane, the g x and g y signals being at 60°and 30°to the membrane, respectively (Blum et al, 1978). The hemes of cytochrome bo 3 have a similar orientation (Salerno and Ingledew, 1991). The EPR resonances of heme a correspond to the in-heme-plane projections of the d xz and d yx orbitals and so approximate to the axes of highest and lowest unpaired electron density.…”

Section: Introductionmentioning

confidence: 99%

Angular Dependences of Perpendicular and Parallel Mode Electron Paramagnetic Resonance of Oxidized Beef Heart Cytochrome c Oxidase

Hunter

Oganesyan

Salerno

et al. 2000

Biophysical Journal

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Cytochrome c oxidase catalyzes the reduction of oxygen to water with a concomitant conservation of energy in the form of a transmembrane proton gradient. The enzyme has a catalytic site consisting of a binuclear center of a copper ion and a heme group. The spectroscopic parameters of this center are unusual. The origin of broad electron paramagnetic resonance (EPR) signals in the oxidized state at rather low resonant field, the so-called g' = 12 signal, has been a matter of debate for over 30 years. We have studied the angular dependence of this resonance in both parallel and perpendicular mode X-band EPR in oriented multilayers containing cytochrome c oxidase to resolve the assignment. The "slow" form and compounds formed by the addition of formate and fluoride to the oxidized enzyme display these resonances, which result from transitions between states of an integer-spin multiplet arising from magnetic exchange coupling between the five unpaired electrons of high spin Fe(III) heme a(3) and the single unpaired electron of Cu(B). The first successful simulation of similar signals observed in both perpendicular and parallel mode X-band EPR spectra in frozen aqueous solution of the fluoride compound of the closely related enzyme, quinol oxidase or cytochrome bo(3), has been reported recently (Oganesyan et al., 1998, J. Am. Chem. Soc. 120:4232-4233). This suggested that the exchange interaction between the two metal ions of the binuclear center is very weak (|J| approximately 1 cm(-1)), with the axial zero-field splitting (D approximately 5 cm(-1)) of the high-spin heme dominating the form of the ground state. We show that this model accounts well for the angular dependences of the X-band EPR spectra in both perpendicular and parallel modes of oriented multilayers of cytochrome c oxidase derivatives and that the experimental results are inconsistent with earlier schemes that use exchange coupling parameters of several hundred wavenumbers.

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Orientation of the haems of the ubiquinol oxidase: O₂ reductase, cytochrome bo of Escherichia coli

Cited by 14 publications

References 14 publications

Transmembrane topology and axial ligands to hemes in the cytochrome b subunit of Bacillus subtilis succinate:menaquinone reductase

Transmembrane topology and axial ligands to hemes in the cytochrome b subunit of Bacillus subtilis succinate:menaquinone reductase

The orientation of the three haems of the ‘in situ’ ubiquinol oxidase, cytochrome bd, of Escherichia coli

Angular Dependences of Perpendicular and Parallel Mode Electron Paramagnetic Resonance of Oxidized Beef Heart Cytochrome c Oxidase

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