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Müller M, Azzi A. Subunit I is the catalytic center of Paracoccus denitrificans cytochrome c oxidase. Ann N Y Acad Sci 1988; 550:13-21. [PMID: 2854385 DOI: 10.1111/j.1749-6632.1988.tb35317.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- M Müller
- Institut für Biochemie und Molekularbiologie der Universität Bern, Switzerland
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Müller M, Schlapfer B, Azzi A. Preparation of a one-subunit cytochrome oxidase from Paracoccus denitrificans: spectral analysis and enzymatic activity. Biochemistry 1988; 27:7546-51. [PMID: 2462906 DOI: 10.1021/bi00419a055] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Cytochrome c oxidase was isolated from Paracoccus denitrificans as a two-subunit enzyme. Chymotrypsin-catalyzed proteolysis reduced the molecular weight of each subunit by about 8000. The spectral properties of this preparation, as well as its Km for cytochrome c(1.7 muM), remained unchanged with respect to the native enzyme. Vmax was reduced by about 55% when assayed in Triton X-100 or in Triton X-100 supplemented with asolectin. Following further proteolysis by Staphylococcus aureus V8 protease, subunit I remained unchanged as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, whereas subunit II was split into small peptides. These were removed by ion-exchange high-performance liquid chromatography. The one-subunit enzyme had an apparent molecular weight of 43,000. The reduction of molecular weight was also confirmed by the diminution of the ultraviolet/Soret absorption ratio. This value was 1.8-2.1 for the native enzyme and 1.3-1.5 for the one-subunit enzyme. The spectral properties (including the spectrum CO reduced minus reduced) were not modified by the proteolytic treatment, indicating that cytochromes a and a3 were present in equal amounts. The lack of spectral alteration and the known close association of the copper B atom with cytochrome a3 suggest that copper B is also contained within the one-subunit enzyme. The Km of the one-subunit oxidase was similar to that of the two-subunit enzyme; Vmax was decreased by about 50%. The activity of the one-subunit oxidase had a salt-dependent maximum at 30 mM KCl, almost identical with that of the undigested enzyme, and was inhibited by micromolar concentrations of KCN.
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Affiliation(s)
- M Müller
- Institut für Biochemie und Molekularbiologie der Universität Bern, Switzerland
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Müller M, Schläpfer B, Azzi A. Cytochrome c oxidase from Paracoccus denitrificans: both hemes are located in subunit I. Proc Natl Acad Sci U S A 1988; 85:6647-51. [PMID: 2842784 PMCID: PMC282034 DOI: 10.1073/pnas.85.18.6647] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The two-subunit cytochrome c oxidase from Paracoccus denitrificans has been sequentially digested with chymotrypsin and Staphylococcus aureus V8 protease. The smaller subunit of the enzyme (apparent Mr 32,000) was split into numerous peptides that were removed by anion-exchange HPLC. The larger subunit was only digested to a limited extent (from an apparent Mr 45,000 to Mr 43,000), and the spectral properties were preserved relative to the native enzyme (a reduced minus oxidized difference spectrum with maxima at 447 and 607 nm in the Soret and alpha region, respectively). As judged from CO-reduced spectra this proteolytically digested, one-fragment oxidase was found to contain an equal amount of cytochromes a and a3. The enzymatic activity with reduced cytochrome c as substrate in the presence of Triton X-100 proceeded with equal affinity (apparent Km = 0.5-1.0 microM) and with a Vmax of approximately 20% (40 s-1) of that found with the native enzyme (200 s-1). When the assay system was supplemented with soybean phospholipids, the Km became 2 microM for both enzymes and the Vmax became 730 and 170 s-1 for the native and the digested enzyme, respectively. Thus subunit I of P. denitrificans oxidase, and most probably of the other cytochrome c oxidases as well, contains both hemes and at least one Cu atom and has significant enzymatic activity.
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Affiliation(s)
- M Müller
- Institut für Biochemie und Molekularbiologie, Universität Bern, Switzerland
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Bolli R, Müller M, Nalecs K, Azzi A. Cytochrome c oxidase: example of a redox-coupled proton pump. Mol Aspects Med 1988; 10:249-55. [PMID: 2852745 DOI: 10.1016/0098-2997(88)90011-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- R Bolli
- Institute of Biochemistry and Molecular Biology, University of Bern, Switzerland
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Yewey GL, Caughey WS. Metals and activity of bovine heart cytochrome c oxidase are independent of polypeptide subunits III, VII, a, and b. Biochem Biophys Res Commun 1987; 148:1520-6. [PMID: 2825690 DOI: 10.1016/s0006-291x(87)80304-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Bovine heart cytochrome c oxidase, depleted of polypeptide subunits by alkaline detergent treatment, was characterized with respect to metal content, optical spectral properties, and oxidase activity. Treatment with 1.0% Triton X-100 at pH 9.5 followed by anion-exchange chromatography caused removal of subunit III, subunit VII, and polypeptides a and b. The metal atom stoichiometries of the control and the polypeptide-depleted enzyme were in both cases 2.5Cu/2Fe/1Zn/1Mg with metal-to-protein ratios significantly greater in the latter. The treated enzyme exhibited a red shifted oxidized Soret maximum and bound carbon monoxide upon reduction. Activity was markedly decreased by the treatment but was restored to control levels by incubation with 0.3% Tween 80 at pH 6.0. Therefore, subunit III, subunit VII, polypeptide a, and polypeptide b do not contain Cu, Fe, Zn, or Mg and are not essential for reduction of O2 by ferrocytochrome c.
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Affiliation(s)
- G L Yewey
- Department of Biochemistry, Colorado State University, Fort Collins 80523
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de Vrij W, Konings WN. Kinetic characterization of cytochrome c oxidase from Bacillus subtilis. EUROPEAN JOURNAL OF BIOCHEMISTRY 1987; 166:581-7. [PMID: 3038545 DOI: 10.1111/j.1432-1033.1987.tb13553.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Bacillus subtilis aa3-type cytochrome c oxidase is capable of oxidizing cytochrome c from different origins. The kinetic properties of the enzyme are influenced by ionic strength. The affinity for Saccharomyces cerevisiae cytochrome c declines with increasing ionic strength whereas the Vmax remains almost constant. An increase of Vmax is observed when the enzyme is incorporated in artificial membranes. Negatively charged phospholipids allow high turnover rates of the aa3-type oxidase. The effect of ionic strength on oxidation of horse heart cytochrome c results in significant changes of both Km and Vmax. These effects can be explained by disturbances of enzyme-substrate interactions and are not related to changes in the aggregation state of the enzyme. The respiration control index of the enzyme reconstituted in artificial membranes appeared to be dependent on phospholipid composition, protein/lipid ratios and also on the external pH. The action of the ionophores nigericin and valinomycin, at various pH values, on the enzyme activity and proton-permeability measurements of the membranes indicate that both components of the proton-motive force, the membrane potential and the pH gradient, can in principle regulate enzyme activity in the reconstituted state.
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Evolution of a Regulatory Enzyme: Cytochrome-c Oxidase (Complex IV). CURRENT TOPICS IN BIOENERGETICS - STRUCTURE, BIOGENESIS, AND ASSEMBLY OF ENERGY TRANSDUCING ENZYME SYSTEMS 1987. [DOI: 10.1016/b978-0-12-152515-6.50009-6] [Citation(s) in RCA: 145] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Hill BC, Greenwood C, Nicholls P. Intermediate steps in the reaction of cytochrome oxidase with molecular oxygen. BIOCHIMICA ET BIOPHYSICA ACTA 1986; 853:91-113. [PMID: 3030416 DOI: 10.1016/0304-4173(86)90006-6] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Rigell CW, de Saussure C, Freire E. Protein and lipid structural transitions in cytochrome c oxidase-dimyristoylphosphatidylcholine reconstitutions. Biochemistry 1985; 24:5638-46. [PMID: 3000433 DOI: 10.1021/bi00341a053] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The thermotropic behavior of the mitochondrial enzyme cytochrome c oxidase (EC 1.9.3.1) reconstituted in dimyristoylphosphatidylcholine (DMPC) vesicles has been studied by using high-sensitivity differential scanning calorimetry and fluorescence spectroscopy. The incorporation of cytochrome c oxidase into the phospholipid bilayer perturbs the thermodynamic parameters associated with the lipid phase transition in a manner analogous to other integral membrane proteins: it reduces the enthalpy change, lowers the transition temperature, and reduces the cooperative behavior of the phospholipid molecules. Analysis of the dependence of the enthalpy change on the protein:lipid molar ratio indicates that cytochrome c oxidase prevents 99 +/- 5 lipid molecules from participating in the main gel-liquid-crystalline transition. These phospholipid molecules presumably remain in the same physical state below and above the transition temperature of the bulk lipid, thus providing a more or less constant microenvironment to the protein molecule. The effect of the phospholipid bilayer matrix on the thermodynamic stability of the cytochrome c oxidase complex was examined by high-sensitivity differential scanning calorimetry. Detergent (Tween 80)-solubilized cytochrome c oxidase undergoes a complex, irreversible thermal denaturation process centered at 56 degrees C and characterized by an enthalpy change of 550 +/- 50 kcal/mol of enzyme complex. Reconstitution of the cytochrome c oxidase complex into DMPC vesicles shifts the transition temperature upward to 63 degrees C, indicating that the phospholipid bilayer moiety stabilizes the native conformation of the enzyme. The lipid bilayer environment contributes approximately 10 kcal/mol to the free energy of stabilization of the enzyme complex. The thermal unfolding of cytochrome c oxidase is not a two-state process.(ABSTRACT TRUNCATED AT 250 WORDS)
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Nałeçz KA, Bolli R, Ludwig B, Azzi A. The role of subunit III in bovine cytochrome c oxidase. Comparison between native, subunit III-depleted and Paracoccus denitrificans enzymes. BIOCHIMICA ET BIOPHYSICA ACTA 1985; 808:259-72. [PMID: 2990554 DOI: 10.1016/0005-2728(85)90008-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In order to obtain information on the role of subunit III in the function and aggregation state of cytochrome c oxidase, the kinetics of ferrocytochrome c oxidation by the bovine cytochrome c oxidase depleted of its subunit III were studied and compared with those of the oxidase isolated from P. denitrificans which contains only two subunits. The aggregation state of both enzymes dispersed in dodecyl maltoside was also compared. The two-subunit oxidase from P. denitrificans gave linear Eadie-Hofstee plots and the enzyme resulted to be monomeric (Mr = 82 000) both, in gel filtration and sucrose gradient centrifugation studies. The bovine heart subunit III depleted enzyme, under conditions when the P. denitrificans cytochrome c oxidase was in the form of monomers, was found to be dimeric by sucrose gradient centrifugation analysis. At lower enzyme concentrations monomers were, however, detected by gel filtration. Depletion of subunit III was accompanied by the loss of small polypeptides (VIa, VIb and VIIa) and of almost all phospholipid (1-2 molecules were left per molecule of enzyme). The electron-transfer activity of the subunit III-depleted enzyme showed a monophasic Eadie-Hofstee plot, which upon addition of phospholipids became non-linear, similar to that of the control bovine cytochrome c oxidase. One of the roles of subunit III may be that of stabilising the dimers of cytochrome c oxidase. Lack of this subunit and loss of phospholipid is accompanied by a change in the kinetics of electron transfer, which might be the consequence of enzyme monomerisation.
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Bolli R, Nałecz KA, Azzi A. The aggregation state of bovine heart cytochrome c oxidase and its kinetics in monomeric and dimeric form. Arch Biochem Biophys 1985; 240:102-16. [PMID: 2990338 DOI: 10.1016/0003-9861(85)90012-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The monomeric and dimeric forms of bovine cytochrome c oxidase (EC 1.9.3.1) were obtained from gel filtration chromatography on Ultrogel AcA 34 and analyzed. Both species contained all 12-13 subunits described for this enzyme. In the dimer 320 molecules [3H]dodecyl-beta-D-maltoside were bound per heme aa3 and in the monomer 360 molecules per heme aa3. The monomers contained 10 mol of tightly bound phospholipid/mol heme aa3 and the dimers 14. Sedimentation coefficients of 15.5-18 S for the dimer and 9.6 S for the monomer were calculated from sucrose density centrifugation analysis and analytical centrifugation. By the laser beam light-scattering technique a Stokes radius of 70 A for the dimeric detergent-lipid-protein complex was measured. From those parameters and the densitometric determined partial specific volumes of the detergent and the enzyme, the molecular weights of 400,000 for the protein moiety of the dimer and 170,000-200,000 for the monomer were calculated. Under very low ionic strength conditions the monomer/dimer equilibrium was found to be dependent on the protein concentration. At low enzyme concentrations (10(-9) M) monomers were predominant, whereas at concentrations above 5 X 10(-6) M the amounts of dimers and higher aggregates were more represented. The cytochrome c oxidase activity, measured spectrophotometrically and analyzed by Eadie-Hofstee plot, was biphasic as a function of cytochrome c concentration for the dimeric enzyme. Pure monomers gave monophasic kinetics. The data, fitting with a homotropic negative cooperative mechanism for the dimer of cytochrome c oxidase, are discussed and compared with other described mechanisms.
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Bolli R, Nałecz KA, Azzi A. The interconversion between monomeric and dimeric bovine heart cytochrome c oxidase. Biochimie 1985; 67:119-28. [PMID: 2986725 DOI: 10.1016/s0300-9084(85)80237-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Monomers and dimers of bovine heart cytochrome c oxidase (EC 1.9.3.1.) were separated by gel filtration chromatography on Ultrogel AcA 34 or by sucrose gradient centrifugation. Factors influencing the interconversion of the two aggregation states of this enzyme were analyzed. At very low ionic strength, in the presence of dodecyl maltoside, monomers were the main species. Salts appeared to stabilize the dimeric form, divalent cations being more efficient than monovalent. High enzyme concentrations favoured the formation of dimers, also at low ionic strength. The type of detergent had a strong influence on the monomer-dimer interconversion; in Triton X-100 and dodecyl maltoside (at high ionic strength) cytochrome c oxidase was homogenously dispersed in its dimeric form, while in Tween-80 gel filtration showed only large particles eluting in the void volume. In cholate monomers and aggregates were observed but no dimers. The aggregation state had an influence on the steady state kinetics of the ferrocytochrome c oxidase activity. Monomers showed linear Eadie-Hofstee plots, whilst the dimeric and aggregated enzyme gave nonlinear Eadie-Hofstee plots. Ionic strength, enzyme concentration and type of detergent were affecting the enzyme's kinetics in a way consistent with the molecular form obtained by the gel filtration or sedimentation analysis. The data support a negative cooperative mechanism for the interaction of cytochrome c with the dimeric enzyme, as proposed earlier (K.A. Nałecz et al., (1983) Biochem. Biophys. Res. Commun., 114, 822-828).
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Azzi A, Casey RP, Nałecz MJ. The effect of N,N'-dicyclohexylcarbodiimide on enzymes of bioenergetic relevance. BIOCHIMICA ET BIOPHYSICA ACTA 1984; 768:209-26. [PMID: 6095905 DOI: 10.1016/0304-4173(84)90017-x] [Citation(s) in RCA: 94] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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