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PubMed1993

Spectroscopic characterization of the interaction of azide and thiocyanate with the binuclear center of cytochrome oxidase: evidence for multiple ligand sites.

The interactions of azide and thiocyanate with the binuclear center of oxidized cytochrome c oxidase have been characterized by Fourier transform infrared and UV-vis spectroscopy, electron paramagnetic resonance and magnetic and natural circular dichroism. Azide binds in two phases, a high-affinity phase (Kd = 64 microM) in which it is bound as a bridge to the binuclear center and a low-affinity phase (Kd = 20 mM) in which it displaces one of the axial ligands to cytochrome a. Thiocyanate also binds in two phases. The high-affinity phase (Kd = 2.7 mM) involves binding in a terminal mode to CuB; the low-affinity phase is complex and involves both CuA and cytochrome a. In contrast to the recent proposal of Yoshikawa and Caughey [(1990) J. Biol. Chem. 265, 7945-7958], we conclude that cyanide also functions as a bridge between cytochrome a3 and CuB. In the presence of cyanide, azide does not bind to its high-affinity site but thiocyanate does bind to its high-affinity site.

Azides↗
PubMed1993

Identity of GABP with NRF-2, a multisubunit activator of cytochrome oxidase expression, reveals a cellular role for an ETS domain activator of viral promoters.

The ETS domain proteins are a diverse family of transcriptional activators that have been implicated recently in the expression of a number of cell-specific and viral promoters. Nuclear respiratory factor 2 (NRF-2) is a nuclear transcription factor that activates the proximal promoter of the rat cytochrome c oxidase subunit IV (RCO4) gene through tandem sequence elements. These elements conform to the consensus for high-affinity ETS domain recognition sites. We have now purified NRF-2 to homogeneity from HeLa cells and find that it consists of five polypeptides, only one of which has intrinsic DNA-binding ability. The others participate in the formation of heteromeric complexes with distinct binding properties. NRF-2 also specifically recognizes multiple binding sites in the mouse cytochrome c oxidase subunit Vb (MCO5b) gene. As in the functionally related RCO4 gene, tandemly arranged NRF-2 sites are essential for the activity of the proximal MCO5b promoter, further substantiating a role for NRF-2 in respiratory chain expression. Determination of peptide sequences from the various subunits of HeLa NRF-2 reveals a high degree of sequence identity with mouse GA-binding protein (GABP), a multisubunit ETS domain activator of herpes simplex virus immediate early genes. A cellular role in the activation of nuclear genes specifying mitochondrial respiratory function is thus assigned to an ETS domain activator of viral promoters.

Amino Acid Sequence↗
PubMed1988

Cytochrome oxidase histochemistry in the rat hippocampus. A quantitative methodological study.

The diaminobenzidine (DAB) method was adapted for the microphotometric determination of cytochrome c oxidase (cyt ox) in the rat hippocampus. The qualitative and quantitative investigations at the light microscopic level showed that acetone and cytochrome c pretreatment of cryostat sections resulted in a significant increase of demonstrable cyt ox activities. The final incubation medium consisted of 7.5 mM DAB, 2% polyvinylalcohol (PVA) and 6% dimethyl sulfoxide in 0.1 M Hepes buffer; final pH 7.5. PVA was used to keep DAB and artificially oxidized DAB in solution. In the kinetic and endpoint measurements a linear response of the reaction with highest slope was observed only in the initial 5-6 min of reaction. Thereafter the slope decreased. Ultracytochemical demonstrations, which were performed as a topochemical control, showed reaction product only in mitochondria (cristae and intermembranous space). In contrast to vibratome sections all mitochondria reacted positively in cryostat sections of aldehyde-fixed hippocampi. The enhancement of reaction after acetone pretreatment of cryostat sections (light microscopic level) and after a freezing step in ultracytochemistry is discussed in connection with diffusion problems of DAB through mitochondrial membranes.

3,3'-Diaminobenzidine↗
PubMed1990

The proteoliposomal steady state. Effect of size, capacitance and membrane permeability on cytochrome-oxidase-induced ion gradients.

1. The flux pathways for H+ and K+ movements into and out of proteoliposomes incorporating cytochrome c oxidase have been investigated as a function of the electrical and geometrical properties of the vesicles. 2. The respiration-induced pH gradient (delta pH) and membrane potential (delta psi) are mutually dependent and individually sensitive to the permeability properties of the membrane. A lowering or abolition of delta psi by the addition of valinomycin increased the steady-state level of delta pH. Conversely, removal of delta pH by the addition of nigericin resulted in a higher steady-state delta psi. 3. Vesicles prepared by sonication followed by centrifugation maintained similar pH gradients at steady state to those in vesicles prepared by dialysis, although the time taken to reach steady state was longer. Higher pH gradients can be induced in non-centrifuged sonicated preparations. 4. No significant differences were found in H+ and K+ permeability between proteoliposomes prepared by dialysis or by sonication. The permeability coefficient of the vesicle bilayers for H+ was 6.1 x 10(-4) cm.s-1 and that for K+ was 7.5 x 10(-10) cm.s-1. An initial fast change in internal pH was seen on the addition of external acid or alkali, followed by a slower, ionophore-sensitive, change. The initial fast phase can be increased by the lipid-soluble base dibucaine and the weak acid oleate. In the absence of ionophores, increasing concentrations of oleate increased the rate of H+ translocation to a level similar to that seen in the presence of nigericin. Internal alkalinization could also be induced by oleate upon the addition of potassium sulphate. 5. The initial, pre-steady-state and steady-state delta pH and delta psi changes can be simulated using a model in which the enzyme responds to both delta pH and delta psi components of the protonmotive force. At steady state, the electrogenic entry of K+ is countered by electroneutral exit via a K+/H+ exchange. 6. The permeability coefficient, PH, calculated from H+ flux under steady-state turnover conditions, was approx. 100 times higher than the corresponding 'passive' measurements of PH. Under conditions of oxidase turnover, the vesicles appear to be intrinsically more permeable to protons.

Animals↗
PubMed2003

The effect of short-term dimethylglycine treatment on oxygen consumption in cytochrome oxidase deficiency: a double-blind randomized crossover clinical trial.

OBJECTIVE: To study the effectiveness of dimethylglycine (DMG) on oxygen consumption (VO(2)) in children with Saguenay-Lac-Saint-Jean cytochrome-c oxidase (SLSJ-COX) deficiency (OMIM 220111). STUDY DESIGN: In a crossover randomized double-blind clinical trial, 5 children with SLSJ-COX deficiency, who were stable and old enough to comply with VO(2) measurement, were treated with placebo or DMG for 3 days, and with the alternate treatment after a 2-week washout period. VO(2) was measured by indirect calorimetry before and after treatment. Dietary caloric intake was calculated for 3 days before each measurement. Mean caloric intakes per day were 1562 and 1342 kcal x m(-2) before and during placebo, 1,336 and 1,380 before and during DMG, respectively. RESULTS: DMG was well tolerated and, in all cases, resulted in markedly increased blood DMG levels (617 + 203 mmol x L(-1)), versus 0 to 2 mmol x L(-1) without treatment. Mean VO(2) was lower after administration of either DMG (-1 +/- 3 mL x min(-1) x m(-2)) or placebo (-6 +/- 4), but neither difference was statistically significant. There was no detectable effect of DMG treatment on blood levels of lactate, pyruvate, bicarbonate, or pH. VO(2) values of patients (range, 101-135 mL x min(-1) x m(-2)) were lower than published norms (150-160 mL x min(-1) x m(-2)). CONCLUSION: This study suggests that treatment with DMG does not substantially change VO(2) in children with SLSJ-COX deficiency.

Child↗
PubMed1996

Ethanol- and diazepam-induced cytochrome oxidase activity in mammillary bodies.

This study aims to analyze the effect of the administration of diazepam and alcohol on cytochrome c oxidase activity (COX) in the mammillary bodies (MB) with a quantitative densitometry method. The histochemical reaction of the COX is used as a reflection of energy consumption. Our results show an increase in the COX activity after treatment with diazepam in the different nuclei of MB: medial medial nucleus (MMNm), lateral medial nucleus (MMN1), and lateral nucleus (LMN) of the MB, the MMNm and LMN being significantly more active compared to the MMN1. Furthermore, the consequences of administering these drugs become manifest in spatial learning (water T maze). The performance in a spatial discrimination task did not prove to be impaired.

Animals↗
PubMed1998

A histochemical demonstration of altered cytochrome oxidase activity in the rat brain by neuroleptics.

Regional alterations in neuronal functional activity were examined in the rat brain using cytochrome-c oxidase (COX) histochemistry following chronic neuroleptic treatment. Haloperidol, fluphenazine, and clozapine were administered to animals for 28 days after which profiles of COX activity were generated. Significant increases in COX activity were evident in area 2 of the frontal cortex of all treated animals. Clozapine and fluphenazine, but not haloperidol, caused significant increases in COX activity in the caudate nucleus, nucleus accumbens, septum, and pontine nucleus. Statistically significant increases in COX activity were also observed in hippocampal CA2 and CA3 subfields in clozapine treated animals. Results offer support for the concept that neuroleptics achieve their therapeutic effects primarily via an enhancement of brain function in the frontal cortex, but also point to other brain regions which may be involved in the actions of these drugs.

Animals↗
PubMed1998

Effects of nitroquine on ultrastructures and cytochrome oxidase of exoerythrocytic Plasmodium yoelii in rat liver.

AIM: To study the effects of nitroquine acetate (NA) on the ultrastructures and cytochrome-c oxidase (CCO) of exoerythrocytic forms (EEF) of Plasmodium yoelii. METHODS: Rats were inoculated with sporozoites directly into the liver. After 48 h rats were killed. Rat liver thin sections were incubated in histochemical reaction medium, then examined by transmission electron microscopy. NA (2 mg.kg-1) was fed to rats 3.5 h and 14 h before killing the rats. RESULTS: At 3.5 h, in the parasites there appeared swelling and proliferation of mitochondria, dilation of endoplasmic reticulum, and reduction of the electron density of parasites' nuclei. The structures of the parasites disintegrated to form many autophagocytes 14 h after exposure to NA. The reaction products of CCO still existed until 14 h after using NA. CONCLUSION: CCO was not the starting point of NA action. NA interferes with the structure and function of the cytoplasm and nucleus of malaria parasites and exerts its antimalarial effects in many aspects.

Animals↗
PubMed2004

Interaction of the bacterial terminal oxidase cytochrome bd with nitric oxide.

Cytochrome bd is a prokaryotic terminal oxidase catalyzing O2 reduction to H2O. The oxygen-reducing site has been proposed to contain two hemes, d and b595, the latter presumably replacing functionally CuB of heme-copper oxidases. We show that NO, in competition with O2, rapidly and potently (Ki = 100 +/- 34 nM at approximately 70 microM O2) inhibits cytochrome bd isolated from Escherichia coli and Azotobacter vinelandii in turnover, inhibition being quickly and fully reverted upon NO depletion. Under anaerobic reducing conditions, neither of the two enzymes reveals NO reductase activity, which is proposed to be associated with CuB in heme-copper oxidases.

Azotobacter vinelandii↗
PubMed1982

Effect of magnetic field on activity of cytochrome oxidase not moved or moved relative to magnetic field lines.

The influence of constant homogeneous magnetic fields (700 to 13,000 gauss) on cytochrome c oxidase activity as a function of strength and duration of magnetic field and as a function of enzyme concentration at 0-5 degrees C in solution was measured on samples not moved or moved relative to the magnetic field lines. Increases or decreases of enzyme activity were observed depending on whether or not the samples were so moved. These changes persisted for hours after terminating exposure to the magnetic field.

Animals↗
PubMed1984

Selective contrast in electron microscopy of crystalline cytochrome oxidase.

We have used various techniques for preparation of specimens for electron microscopy in order to selectively contrast different regions of vesicle crystals of cytochrome c oxidase dimers. The results are consistent with a dimer composed of two y-shaped monomers [Fuller et al., J. Mol. Biol. 134 (1979) 305] aligned along one pair of arms with the other pair of arms approximately 70 A apart. The four arms of the monomers lie within and perpendicular to the lipid bilayer in which the dimer is embedded, and the arms protrude approximately 25 A from the lipid bilayer on the matrix side of the membrane. The cytoplasmic side domains of the two monomers split away from one another forming a large cleft in the dimer. Monovalent antibodies (Fab fragments) to subunit IV appear to bind to the two monomer arms which are closely apposed across the two-fold axis of the dimer.

Crystallography↗