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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Detergent-solubilized bovine heart cytochrome c oxidase requires 2 mol of tightly bound cardiolipin (CL) per mole of monomeric complex for functional activity. Four lines of evidence support this conclusion: (1) Phospholipid depletion shows that two tightly bound CL's must remain associated with cytochrome c oxidase in order to maintain full electron transport activity. (2) Removal of the two tightly bound CL's correlates with decreased activity that is restored by reassociation of 2 mol of exogenous CL. (3) CL-depleted cytochrome c oxidase has two high-affinity binding sites for 2-[14C]acetylcardiolipin (AcCL), Kd,app less than 0.1 microM, that are not present in enzyme containing endogenous CL. An additional 2-3 lower affinity AcCL binding sites, Kd,app = 4 microM, are present in the CL-depleted complex, but these sites are also present in enzyme containing endogenous CL. (4) CL, monolysocardiolipin (MLCL), and dilysocardiolipin (DLCL) compete for AcCL binding with approximately the same relative affinities as those measured by the restoration of electron transport activity (MLCL competes much better than DLCL). However, MLCL and DLCL are only 60% and 15% as effective as CL in restoring maximum activity when they are bound to the high-affinity sites. The binding specificity of CL, MLCL, DLCL, and some of their acylated derivatives indicates that the apolar tails are most important for binding, not the polar head group. The presence or absence of hydroxyl groups in CL, MLCL, or DLCL also has little effect upon binding affinities. Binding specificity clearly favors CL since phosphatidylglycerol, phosphatidic acid, and phosphatidylcholine each have very low affinity for the CL binding sites (Kd,app greater than 20 microM). We, therefore, conclude that restoration of activity to CL-depleted cytochrome c oxidase is highly specific and requires the reassociation of CL, or structurally similar compounds, with two high-affinity binding sites.
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PMID:Cardiolipin-depleted bovine heart cytochrome c oxidase: binding stoichiometry and affinity for cardiolipin derivatives. 217 38

Valinomycin binds to soluble and reconstituted cytochrome c oxidase (COX) in a stoichiometric manner, as shown by a spectral shift of the oxidized gamma-band. No spectral change is found with nigericin or 18-crown-6 and in the absence of potassium ions. Titration of the proton pumping activity of reconstituted COX with valinomycin reached a maximum of H+/e- - 0.73 after addition of 1 mole of valinomycin per mole of reconstituted COX. It is concluded that K+-translocation in proton-pumping COX vesicles occurs via enzyme-bound valinomycin.
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PMID:Valinomycin binds stoichiometrically to cytochrome c oxidase and changes its structure and function. 247 18

The endogeneous lipid of bovine heart cytochrome c oxidase has been replaced by dimyristoylphosphatidylcholine using cholate-mediated exchange. The lipid-substituted preparation contained less than 1 mole cardiolipin per mole enzyme and possessed full oxidative activity. The association of spin-labelled cardiolipin with such lipid-substituted cytochrome oxidase preparations has been assayed using ESR spectroscopy. An average relative association constant 5.4-times that for phosphatidylcholine is obtained for cardiolipin. Measurements on preparations with increasing contents of unlabelled cardiolipin, introduced during lipid exchange, reveal that this selectivity corresponds to a generalized increase in specificity for all lipid association sites on the protein.
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PMID:Association of spin-labelled cardiolipin with dimyristoylphosphatidylcholine-substituted bovine heart cytochrome c oxidase. A generalized specificity increase rather than highly specific binding sites. 298 13

A series of amine-specific reagents based on the benzaldehyde reactive group have been synthesized, characterized, and used to study beef heart cytochrome c oxidase reconstituted in phospholipid bilayers. The series contained three classes of reagents: lipid-soluble phosphodiesters having a single hydrocarbon chain, phospholipid analogues, and a water-soluble benzaldehyde. All reagents were either radiolabeled or spin-labeled or both. The Schiff bases formed by these benzaldehydes with amines were found to be reversible until the addition of the reducing agent sodium cyanoborohydride, whereas attachment of lipid-derived aliphatic aldehydes was not readily reversible in the absence of the reducing agent. The benzaldehyde group provides a convenient method of controlling and delaying permanent attachment to integral membrane proteins until after the reconstitution steps. This ensures that the lipid analogues are located properly to identify amine groups at the lipid-protein interface rather than reacting indiscriminately with amines of the hydrophilic domains of the protein. The benzaldehyde lipid labels attach to cytochrome c oxidase with high efficiency. Typically, 20% of the amount of lipid label present was covalently attached to the protein, and the number of moles of label incorporated per mole of protein ranged from 1 to 6, depending on the molar ratios of label, lipid, and protein. The efficiency of labeling by the water-soluble benzaldehyde was much less than that observed for any of the lipid labels because of dilution effects, but equivalent levels of incorporation were achieved by increasing the label concentration. Electron spin resonance spectra of a nitroxide-containing phospholipid analogue covalently attached to reconstituted cytochrome c oxidase exhibited a large motion-restricted component, which is characteristic of spin-labeled lipids in contact with the hydrophobic surfaces of membrane proteins. The line shape and splittings were similar for covalently attached label and label free to diffuse and contact the protein molecules in the bilayer, providing independent evidence that the coupling occurs at the protein-lipid interface. The distribution of the benzaldehyde reagents attached to the polypeptide components of cytochrome c oxidase was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The labeling pattern observed for the lipid analogues was not affected by the presence of the nitroxide moiety on the acyl chains but was dependent on the molar ratio of labeling reagent to protein.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Identifying regions of membrane proteins in contact with phospholipid head groups: covalent attachment of a new class of aldehyde lipid labels to cytochrome c oxidase. 300 51

The reaction of a copper(II) or nickel(II) imidazolate complex (M[CBP-PHEN-4-CHO-Im]) with zinc(II)tetraphenylporphyrin (TPP) in toluene results in the formation of an imidazolate bridged heterobinuclear axial adduct. Conversion of the four-coordinated Zn(TPP) to the five-coordinated species is followed in the visible region between 700 and 500 nm. Isosbestic behavior is exhibited at 523, 556, 588, and 638 nm by solutions of Zn(TPP) to which varying amounts of the metal imidazolate complex are added, indicating the existence of an equilibrium between Zn(TPP) and its axial adduct. The products exhibit maxima beta and alpha bands at 566 and 606 nm, respectively, which are red-shifted from 548 and 588 nm for Zn(TPP) and yield epsilon alpha/epsilon beta ratios of 0.57 and 0.55 for the Ni(II) and Cu(II) adducts, respectively. The binding of the metal imidazolate complexes is thought to closely resemble that of N-methylimidazole, N-CH3Im, rather than imidazolate, owing to the close spectral similarities with the adduct of the former and significant differences from the latter. Formation constants were determined using the 548-nm beta band of Zn(TPP) in the 293-308 K range by the method of Rose and Drago. At 25 degrees C, K = 152,000 M-1 and 110,000 M-1 for the copper and nickel adducts, respectively. Comparison of these values to that of 54,100 M-1 for N-CH3Im indicates that the metal-imidazolate complexes are considerably more reactive. Van't Hoff plots for the two series are very similar with enthalpies of -41.9 and -43.3 kJ/mole respectively. The structural core of these complexes is similar to the imidazolate bridged model of cytochrome c oxidase in that they contain a metal imidazolate axially adducted to a metalloporphyrin.
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PMID:Imidazolate bridged heterobinuclear complexes of zinc(II)tetraphenylporphyrin. Modeling cytochrome c oxidase. 301 87

The interaction of mitochondrial creatine kinase and ATP-ADP translocase with 2.3-dialdehyde derivatives of ADP and ATP (oADP and oATP) has been studied. It was shown that these compounds are irreversible and specific inhibitors of creatine kinase (KioADP = 0.6mM, KioATP = 1.12 mM) and ATP-ADP translocase (KioADP = 0.065mM, KioATP = 0.14 mM). The substrates protect both enzymes from inactivation by these compounds. The maximal pseudo-first order rate constants for the 2,3-dialdehyde nucleotide derivative interaction with creatine kinase are 0.2 min-1 for oADP (pH 6.5) and 0.11 min-1 for oATP (pH 7.0). A decrease in the creatine kinase activity correlates with the incorporation of the reagent into the protein. The completely inactivated, isolated and purified enzyme contains 1 mol of oADP per mole of active sites. A procedure for simultaneous determination of the creatine kinase and translocase content in mitochondria and mitoplasts has been developed, which is based on the application of [3H]oADP in combination with specific treatment of mitochondria (or mitoplasts) with carboxyatractyloside 2,4-dinitrofluorobenzene and a mixture of creatine kinase substrates (MgADP + phosphocreatine). It has been found that for heart mitochondria from different animals the content of creatine kinase and translocase is 2.1-2.6 and 2.4-2.9 mol per mol of cytochrome c oxidase, respectively. Thus, the stoiochiometric ratio of creatine kinase and ATP-ADP translocase is close to 1.0 for all mitochondrial preparations under study (i.e. rat, dog, rabbit and chicken).
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PMID:[Affinity modification of creatine kinase and ATP-ADP translocase in heart mitochondria: determination of their stoichiometric ratio]. 302 Dec 43

The maximal content of mitochondrial isoenzyme of creatine kinase (CK) in rat heart mitochondria does not exceed 12.5 moles per mole of ATP-ADP translocase. This value was obtained by titration of mitochondrial CK activity in aged mitochondria by 5,5'-dithiobis-(2-nitrobenzoate) (DTNB) and 2,4-dinitrofluorobenzene (DNFB) and by a more complex and accurate method. The essential thiol groups of membrane-bound mitochondrial CK (and its enzymic activity) can be specifically protected by phosphocreatine (12 mM) + ADP (1-5 mM) against inactivation by DTNB. Mitochondria with protected SH-groups of CK and with groups inactivated by DTNB were repeatedly incubated with DTNB under identical conditions and the number of additionally reacted sulfhydryl groups and the changes in CK activity were measured. The differences in the number of additionally reacted SH-groups correlated with the changes in the CK activity, which made it possible to calculate the molar ratios of mitochondrial CK to cytochrome c oxidase and ATP-ADP translocase (2.16 +/- (0.4): 1:2, respectively).
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PMID:[Determination of molar content of creatine kinase in heart mitochondria by SH-reagents]. 627 Dec 62

1. The cytochrome content of beef liver mitochondria differs from that of beef heart mitochondria by an eightfold lower cytochrome aa3 and a twofold lower cytochrome b and c + c1 content. 2. The kinetic properties of cytochrome c oxidases from beef liver and heart were measured with intact cytochrome c-depleted membranes, deoxycholate-dissolved membranes, and with the isolated enzymes at various cytochrome c concentrations with an oxygen electrode. Under all conditions a higher V was found for the liver enzyme, both for the low-affinity and for the high-affinity binding site for cytochrome c. Differences were also found for the Km of the two enzymes. 3. Isolated beef heart mitochondria contained about twice as much cardiolipin than beef liver mitochondria. The isolated enzymes contained one mole cardiolipin per mole of the heart enzyme, but 2 moles cardiolipin per mole of the liver enzyme. 4. By application of a high performance sodium dodecylsulfate gel electrophoretic system the two isolated enzymes could be separated into 13 different protein components, three of which (polypeptides VIa, VIIa and VIII) were found to differ in their apparent molecular weights. The functional meaning of cytochrome c oxidase isoenzymes in liver and heart is discussed.
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PMID:Kinetic and structural differences between cytochrome c oxidases from beef liver and heart. 628 12

The interaction of xanthomegnin, a quinone pigment, with the mitochondrial respiratory chain was demonstrated. Xanthomegnin was reduced by succinate, in the presence of submitochondrial particles or mitochondria, only after all oxygen had been consumed in the system, and the reduction was inhibited by antimycin A or KCN. Xanthomegnin was immediately reduced by NADH in a similar system, the reduced xanthomegnin was reoxidized by oxygen but the reduction by NADH was not inhibited by antimycin A or KCN. Xanthomegnin was also immediately reduced by NADH catalyzed by a purified particulate NADH dehydrogenase complex showing a molar ratio of 2 moles NADH for one mole of xanthomegnin. Reoxidation of the reduced pigment by oxygen occurred in this system. Oxygen consumption was accelerated when xanthomegnin was added to a reaction medium containing NADH, NADH segment and cytochrome c oxidase. Subsequent addition of cytochrome c resulted in a further marked acceleration of oxygen consumption. These results suggest that xanthomegnin interacts with the NAD-linked respiratory chain to produce a xanthomegnin shunt, but this does not occur with the succinate-linked chain.
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PMID:The interaction of a quinone pigment, xanthomegnin, with the mitochondrial respiratory chain. 726 94

Oxygen consumption, ATP production and cytochrome c oxidase activity of isolated mitochondria from body-wall tissue of Arenicola marina were measured as a function of sulphide concentration, and the effect of inhibitors of the respiratory complexes on these processes was determined. Concentrations of sulphide between 6 and 9 µmol l-1 induced oxygen consumption with a respiratory control ratio of 1.7. Production of ATP was stimulated by the addition of sulphide, reaching a maximal value of 67 nmol min-1 mg-1 protein at a sulphide concentration of 8 µmol l-1. Under these conditions, 1 mole of ATP was formed per mole of sulphide consumed. Higher concentrations of sulphide led to a decrease in ATP production until complete inhibition occurred at approximately 50 µmol l-1. The production of ATP with malate and succinate was stimulated by approximately 15 % in the presence of 4 µmol l-1 sulphide, but decreased at sulphide concentrations higher than 15­20 µmol l-1. Cytochrome c oxidase was also inhibited by sulphide, showing half-maximal inhibition at 1.5 µmol l-1 sulphide. Sulphide-induced ATP production was inhibited by antimycin, cyanide and oligomycin but not by rotenone or salicylhydroxamic acid. The present data indicate that sulphide oxidation is coupled to oxidative phosphorylation solely by electron flow through cytochrome c oxidase, whereas the alternative oxidase does not serve as a coupling site. At sulphide concentrations higher than 20 µmol l-1, oxidation of sulphide serves mainly as a detoxification process rather than as a source of energy.
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PMID:Sulphide oxidation and oxidative phosphorylation in the mitochondria of the lugworm 931 82


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