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At least 109 records · Page 6Linked to original sources
PubMed1977

The reactivity to N-ethyl maleimide of the subunits of cytochrome oxidase.

Beef heart cytochrome oxidase (EC 1.9.3.1) prepared in this laboratory consistently presents 10 Coomassie blue staining zones on SDS-polyacrylamide gel electrophoresis. At pH 7.0 only two of these polypeptides (III and VIa) are labelled by radioactive N-ethyl maleimide (NEM). The labelling of VIa is variable and correlates with activity of particular oxidase preparations. When cytochrome oxidase is isolated from alkylated membranes, either mitochrondria or electron transport particles, polypeptide VIa is found not to be labelled; polypeptide III is more strongly labelled than when isolated oxidase is alkylated, and label now appears in polypeptide I which is not alkylated upon treatment of isolated oxidase with NEM.

Animals↗
PubMed2002

Methylene blue restores spatial memory retention impaired by an inhibitor of cytochrome oxidase in rats.

Cytochrome oxidase is the mitochondrial enzyme that catalyzes the utilization of oxygen for the electron transport chain during cellular respiration. Chronic subcutaneous infusion of sodium azide, an inhibitor of cytochrome oxidase, produced a spatial memory retention deficit in rats in a holeboard maze. Methylene blue, which has been shown to increase oxygen consumption in vitro, was used to restore mitochondrial electron transport in order to facilitate memory consolidation. Administration of 1 mg/kg methylene blue after training, during the memory consolidation period, completely restored the memory retention impaired by the inhibitor of cytochrome oxidase. This suggests that methylene blue may compensate for impaired mitochondrial respiration and improve spatial memory retention. Memory retention deficits found in some neurodegenerative diseases may be improved by drugs targeting impaired mitochondrial respiration.

Analysis of Variance↗
PubMed1983

Proton pumping and oxidase activity of thermophilic cytochrome oxidase remain after its extensive proteolysis.

A proton-pumping heme aa3-type cytochrome oxidase purified from the thermophilic bacterium PS3 was treated with trypsin, thermolysin, chymotrypsin, subtilisin, or pronase. The cleavage of the oxidase subunits and the effects of their cleavage on the oxidase activity and proton-pumping in reconstituted vesicles were studied. Trypsin and thermolysin cleaved some of the oxidase subunits without affecting the proton-pumping, but subtilisin and pronase cleaved all the subunits resulting in partial decrease in both activities. Chymotrypsin had an intermediate effect. Subunit II of this enzyme contains heme c which is also cleaved by proteases.

Bacteria↗
PubMed1989

Internal frameshifts within the mitochondrial genes for cytochrome oxidase subunit II and maxicircle unidentified reading frame 3 of Leishmania tarentolae are corrected by RNA editing: evidence for translation of the edited cytochrome oxidase subunit II mRNA.

The Leishmania tarentolae cytochrome oxidase (EC 1.9.3.1) subunit II (COII) and maxicircle unidentified reading frame 3 (MURF3) mRNAs are edited internally by the addition of four and five uridine residues, respectively, which eliminate -1 and +1 reading frameshifts in the gene sequences. The editing events in COII are conserved in three kinetoplastid species, and those in MURF3 are conserved in two species. A primer extension assay showed that the ratio of edited to unedited RNA differed for each gene: 89% of the COII and 36% of the MURF3 transcripts are edited. Preliminary evidence was obtained for translation of the edited COII transcript into protein: antibodies generated against a synthetic peptide with the predicted carboxyl-terminal amino acid sequence reacted with a polypeptide of the correct molecular weight in immunoblots of a mitochondrial lysate.

Amino Acid Sequence↗
PubMed1982

Models of the two heme centers in cytochrome oxidase. The optical properties of cytochrome a and a3.

High and low spin complexes of ferric and ferrous heme a have been prepared and characterized spectroscopically. Bis(1-methylimidazole) heme a provides a good model for cytochrome a in both oxidation states while several spectral properties of cytochrome a3 can be reproduced by 1,2-dimethylimidazole heme a3. The visible absorbance spectra of these analogs account well for the absorbance spectra of oxidized and reduced cytochrome oxidase and support the conclusion (Vanneste, W. (1966) Biochemistry 5, 838-848) that cytochrome a provides the major contribution to the spectral changes in the 600 nm band upon reduction. The 655 nm band present in cytochrome oxidase appears to be a characteristic of high spin heme a+3.

Animals↗
PubMed1985

Resonance raman spectra of CN--bound cytochrome oxidase: spectral isolation of cytochromes a2+, a3(2+), and a3(2+)(CN-).

Reduced cyanide-bound cytochrome oxidase in the absence of any oxygen gives a resonance Raman spectrum consistent with that expected for low-spin heme a. Thus, in contrast to prior reports, ligand binding of cytochrome a3 to form a six-coordinate low-spin ferrous heme does not result in any unusual electronic structure, hydrogen bonding, environment, or conformation of the formyl group. It appears unlikely that there are any changes in this group in cytochrome a3 that control the ligand affinity or redox potential in physiological forms of the ferrous enzyme. With the use of our difference spectrometer and by appropriately selecting the laser excitation frequency, we are able to isolate spectrally cytochromes a2+, a3(2+), and a3(2+)(CN-). The addition of a small amount of oxygen to a preparation of the cyanide-bound reduced enzyme results in a complex with the same Raman spectrum as that previously reported to originate from the cyanide-bound reduced complex. Any oxygen present in the sample leads to enzyme turnover resulting in a mixed valence state [a2+a3(3+)(CN-)]. The comparison between the data on the cyanide-bound reduced enzyme and the data on the CO-bound reduced enzyme illustrates that cyanide binding affects only the modes that respond to the spin state of the ferrous iron, while CO binding affects vibrational modes that respond to a pi-electron density change as well.

Animals↗
PubMed2004

The role of the LRPPRC (leucine-rich pentatricopeptide repeat cassette) gene in cytochrome oxidase assembly: mutation causes lowered levels of COX (cytochrome c oxidase) I and COX III mRNA.

Leigh syndrome French Canadian (LSFC) is a variant of cytochrome oxidase deficiency found in Québec and caused by mutations in the LRPPRC (leucine-rich pentatricopeptide repeat cassette) gene. Northern blots showed that the LRPPRC mRNA levels seen in skeletal muscle>heart>placenta>kidney>liver>lung=brain were proportionally almost opposite in strength to the severity of the enzymic cytochrome oxidase defect. The levels of COX (cytochrome c oxidase) I and COX III mRNA visible on Northern blots were reduced in LSFC patients due to the common (A354V, Ala354-->Val) founder mutation. The amount of LRPPRC protein found in both fibroblast and liver mitochondria from LSFC patients was consistently reduced to <30% of control levels. Import of [(35)S]methionine LRPPRC into rat liver mitochondria was slower for the mutant (A354V) protein. A titre of LRPPRC protein was also found in nuclear fractions that could not be easily accounted for by mitochondrial contamination. [35S]Methionine labelling of mitochondrial translation products showed that the translation of COX I, and perhaps COX III, was specifically reduced in the presence of the mutation. These results suggest that the gene product of LRPPRC, like PET 309p, has a role in the translation or stability of the mRNA for mitochondrially encoded COX subunits. A more diffuse distribution of LRPPRC in LSFC cells compared with controls was evident when viewed by immunofluorescence microscopy, with less LRPPRC present in peripheral mitochondria.

Autopsy↗
PubMedDate not supplied

Effect of impulse blockage on cytochrome oxidase activity in monkey visual system.

Cytochrome oxidase (cytochrome c oxidase; ferrocytochrome c: oxygen oxidoreductase, EC 1.9.2.1) has been introduced as an oxidative metabolic marker for neurones in the central nervous system. Previous studies have shown that mature neurones remained sensitive to altered functional demands, and that both developing and adult neurones responded to sensory deprivation or deafferentation by reducing their cytochrome oxidase (Cyt. Ox.) activity. More recently, we showed that the blockage of retinal impulse transmission with tetrodotoxin led to a reversible reduction in Cyt. Ox. staining of affected lateral geniculate (LGN) and striate neurones in adult cats. The present study sought to extend these findings to adult monkeys, where Cyt. Ox. 'puffs' or 'blobs' are uniquely present in the visual cortex. We found that, while the retina remained histologically intact, with only moderate decreases in Cyt. Ox. staining of large ganglion cells and the two plexiform layers, subtle changes occurred in the LGN as early as 1 day post-tetrodotoxin injection, and clear reduction in enzyme levels was evident in both the LGN and the visual cortex by 3 days. Changes became progressively more severe up to 4 weeks post-injection. Within area 17, alternating bands of high and low Cyt. Ox. staining occurred in lamina IV, with alternating rows of dark and lightly reactive puffs superimposed in exact register. Thus, the mature visual neurones in the primate remain extremely sensitive to the cessation of retinal impulse transmission, and plastic metabolic changes occur through several synapses along the sensory pathway.

Animals↗
PubMed1981

The partially reduced species present in purified cytochrome oxidase from baker's yeast is cytochrome a.

Cytochrome oxidase purified from baker's yeast submitochondrial particles is found to exist in a partially reduced state in the resting enzyme. Studies utilizing optical and EPR spectroscopy indicate that the "inactive" fraction contains a reduced low-spin heme, cytochrome a possibly indicating a block of electron transfer from cytochrome a to cytochrome a 3. There is no apparent reduction of either the EPR-detectable copper or the species associated with the 830 nm band. Oxidative titrations of the resting-state yeast cytochrome oxidase indicate that the reduction potential of the species titrating is higher than that of ferricyanide. This "inactive" cytochrome oxidase is not the result of the isolation procedure, but seems to represent a species which is present in the intact yeast.

Cytochrome a Group↗
PubMed1983

[Reaction of oxidized cytochrome oxidase with cyanide. Effects of pH, cytochrome c and membrane environment].

Binding of HCN with ferric beef heart cytochrome oxidase has been studied in submitochondrial particles, as with the enzyme solubilized in detergent or reconstituted into proteoliposomes. Under all conditions, the reaction proceeds via an intermediate and its kinetics can be described by formal parameters Km and kmax in keeping with the Michaelis-type equation. Km of the reaction strongly depends on the enzyme environment; thus it increases 100-1000 fold upon solubilization of cytochrome oxidase but can be subsequently decreased by incorporation of the enzyme in liposomes and by addition of cytochrome c. pH-dependence of the reaction rate shows that, in submitochondrial particles and proteoliposomes as well as in the case of solubilized enzyme supplement with cytochrome c, HCN specifically binds the form of cytochrome oxidase in which a heme-linked ionizable group with pKa 6,5-6,9 is protonated.

Animals↗
PubMed1995

Degradation of cytochrome oxidase subunits in mutants of yeast lacking cytochrome c and suppression of the degradation by mutation of yme1.

We have confirmed by spectral analysis that cytochrome oxidase is not present in strains of the yeast Saccharomyces cerevisiae having a primary deficiency in cytochrome c, and we have demonstrated by immunological procedures that such strains lack the mitochondrially encoded subunits I, II, and III of cytochrome oxidase. Furthermore, pulse-chase experiments demonstrated that subunit II is rapidly degraded in vivo. This degradation can be at least partially suppressed by disruption of the nuclear gene YME1, which encodes a putative ATP-Zn(2+)-dependent protease. We suggest that the cytochrome oxidase subunits are not properly assembled in the absence of cytochrome c, and that Yme1 and possibly other proteases degrade the unassembled mitochondrial-encoded subunits of cytochrome oxidase.

ATP-Dependent Proteases↗
PubMed1978

Cytochrome c-cytochrome oxidase interaction at subzero temperatures.

Cytochrome oxidase forms two distinctive compounds with oxygen at --105 and --90 degrees C, one appears to be oxycytochrome oxidase (Compound A) and the other peroxycytochrome oxidase (Compound B). The functional role of compound B in the oxidation of cytochrome c has been examined in a variety of mitochondrial preparations. The rate and the extent of the reaction have been found to be dependent upon the presence of a fluid phase in the vicinity of the site of the reaction of cytochrome c and cytochrome oxidase. The kinetics of cytochrome c oxidation and of the slowly reacting component of cytochrome oxidase are found to be linked to one another even in cytochrome c depleted preparations, but under appropriate conditions, especially low temperatures, the oxidation of cytochrome c precedes that of this component of cytochrome oxidase. Based upon the identification of the slowly reacting components of cytochrome oxidase with cytochrome c, various mechanisms are considered which allow cytochrome c to be oxidized without the intervention of cytochrome a at very low temperatures, and tunneling seems an appropriate mechanism.

Animals↗