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PubMed2001

Increase in cytochrome oxidase activity in regenerating nerve fibers of hemitransected spinal cord in the rat.

We explored the possibility of cytochrome oxidase (CO) involvement in spinal cord regeneration in adult rats. The spinal cord was hemitransected at T9. After one month's survival, the animals were deeply anesthetized and perfused. The spinal cord segments including the lesion site were removed and sectioned horizontally for CO histochemistry. Under light microscope, a substantial number of CO-reactive nerve fibers and boutons were identified in the lateral funiculus adjacent to the lesion site. Under electron microscope, moderately to highly CO-reactive mitochondria could be seen within nerve fibers and boutons. Synaptic contacts were identified among them. The increase in CO activity in nerve fibers and boutons may indicate their high-energy demand for synaptic and spontaneous activity following spinal cord hemisection.

Animals↗
PubMed2001

Mapping of mitochondrial metabolic competence by cytochrome oxidase and succinic dehydrogenase cytochemistry.

To map the mitochondrial capacity to provide adenosine triphosphate (ATP), the activities of cytochrome oxidase (COX) and succinic dehydrogenase (SDH) were respectively evidenced by diaminobenzidine (DAB) and copper ferrocyanide cytochemical techniques in the cerebellar cortex of adult rats. Sampling of the positive mitochondria was carried out by the disector procedure. The ratio (R) overall area of the precipitates due to COX activity within the single mitochondrion/area of the same organelle was automatically calculated to estimate enzyme activity vs mitochondrial size. The number of SDH-positive mitochondria/microm(3) of tissue (numeric density, Nv) was morphometrically calculated. Cytochemistry of key enzymes of the respiratory chain enables measurement of the actual capacity of individual mitochondria to provide ATP. This quantitative estimation allows morphofunctional mapping of the mitochondrial metabolic competence in discrete tissue and/or cellular compartments. (J Histochem Cytochem 49:1191-1192, 2001)

Animals↗
PubMed1984

Changes in cytochrome oxidase activity of the rabbit olfactory cortex following unilateral olfactory bulbectomy.

The effects of unilateral olfactory bulbectomy on cytochrome oxidase (CO) activity in the olfactory cortex were studied in adult rabbits. In intact rabbits, layer Ia of the olfactory cortex stained symmetrically for CO activity as a continuous brown band. In animals with unilateral lesion of the olfactory bulb (OB), a great decrease in the level of CO activity was found in layer Ia ipsilaterally. The change became prominent about 12 hr after OB lesion. Thereafter no further decrease in CO activity was observed up to 6 months. A decrease in the level of CO activity was observed in only the denervated lamina to which the OB neurons project directly, but not along the synaptic chain in the olfactory cortex.

Animals↗
PubMed1990

Patterns of cytochrome oxidase activity in the visual cortex of a South American opossum (Didelphis marsupialis aurita).

The normal pattern of cytochrome oxidase (CO) activity in the posterior cortical areas of the South American opossum (Didelphis marsupialis aurita) was assessed both in horizontal sections of flattened cortices and in transversal cortical sections. The tangential distribution of CO activity was uniformly high in the striate cortex. In the peristriate region alternating bands of dense and weak staining occupied all the cortical layers with the exception of layer I. This observation suggests the existence of a functional segregation of visual processing in the peristriate cortex of the opossum similar to that present in phylogenetically more recent groups.

Animals↗
PubMed1985

Selective labeling of beef heart cytochrome oxidase subunit III with eosin-5-maleimide.

Cytochrome c oxidase has been isolated from beef heart mitochondria and labeled with the fluorochrome eosin-5-maleimide (EMA) after pretreatment with mersalyl. On SDS-polyacrylamide gels, EMA fluorescence and absorption occurred at a single band corresponding to subunit III. Since only Cys 115 of the two cysteinyl residues of subunit III had been shown to be reactive towards water-soluble SH-reagents, it was concluded that this residue was the one labeled by EMA. The EMA/enzyme ratio was about 1. Gel filtration experiments have shown that upon treatment with dicyclohexylcarbodiimide, subunit III was loosened from the complex; this result suggests that the inhibitory effect of dicyclohexylcarbodiimide on the H+-translocation activity may be related to such a phenomenon.

Animals↗
PubMed1986

Redox-linked proton translocation in cytochrome oxidase: the importance of gating electron flow. The effects of slip in a model transducer.

In at least one component of the mitochondrial respiratory chain, cytochrome c oxidase, exothermic electron transfer reactions are used to drive vectorial proton transport against an electrochemical hydrogen ion gradient across the mitochondrial inner membrane. The role of the gating of electrons (the regulation of the rates of electron transfer into and out of the proton transport site) in this coupling between electron transfer and proton pumping has been explored. The approach involves the solution of the steady-state rate equations pertinent to proton pump models which include, to various degrees, the uncoupled (i.e., not linked to proton pumping) electron transfer processes which are likely to occur in any real electron transfer-driven proton pump. This analysis furnishes a quantitative framework for examining the effects of variations in proton binding site pKas and metal center reduction potentials, the relationship between energy conservation efficiency and turnover rate, the conditions for maximum power output or minimum heat production, and required efficiency of the gating of electrons. Some novel conclusions emerge from the analysis, including: An efficient electron transfer-driven proton pump need not exhibit a pH-dependent reduction potential; Very efficient gating of electrons is required for efficient electron transfer driven proton pumping, especially when a reasonable correlation of electron transfer rate and electron transfer exoergonicity is assumed; and A consideration of the importance and possible mechanisms of the gating of electrons suggests that efficient proton pumping by CuA in cytochrome oxidase could, in principle, take place with structural changes confined to the immediate vicinity of the copper ion, while proton pumping by Fea would probably require conformational coupling between the iron and more remote structures in the enzyme. The conclusions are discussed with reference to proton pumping by cytochrome c oxidase, and some possible implications for oxidative phosphorylation are noted.

Electron Transport↗
PubMed2002

The rate of internal heme-heme electron transfer in cytochrome C oxidase.

Cytochrome c oxidase catalyzes the one-electron oxidation of four molecules of cytochrome c and the four-electron reduction of dioxygen to water. The process involves a number of intramolecular electron-transfer reactions, one of which takes place between the two hemes of the enzyme, hemes a and a3, with a rate of approximately 3 x 10(5) s(-1) (tau approximately 3 micros). In a recent report [Verkhovsky et al. (2001) Biochim. Biophys. Acta 1506, 143-146], it was suggested that the 3 x 10(5) s(-1) electron transfer may be controlled by structural rearrangements and that there is an additional electron transfer that is several orders of magnitude faster. In the present study, we have reinvestigated the spectral changes occurring in the nanosecond and microsecond time frames after photolysis of CO from the fully reduced and mixed-valence enzymes. On the basis of the differences between them, we conclude that in the bovine enzyme the microscopic forward and reverse rate constants for the electron-transfer reactions from heme a to heme a3 are not faster than approximately 2 x 10(5) and approximately 1 x 10(5) s(-1), respectively.

Animals↗
PubMed1984

Cytochrome a3 structure in carbon monoxide-bound cytochrome oxidase.

The iron-carbon monoxide stretching mode and the iron-carbon-oxygen bending mode in carbon monoxide-bound cytochrome oxidase have been assigned at 520 and 578 cm-1, respectively. The frequencies, widths, and intensities of these modes show that the Fe-C-O grouping in carbon monoxide-cytochrome a3 is linear but tilted from the normal to the heme plane; that the iron-histidine bond in both five- and six-coordinate cytochrome a3 is strained; and that the carbon monoxide and the proximal histidine each have characteristic, well-defined orientations in all molecules. These data can account for the binding affinities of carbon monoxide and dioxygen under physiological conditions.

Animals↗
PubMed1995

Rapid electron injection into multisite metalloproteins: intramolecular electron transfer in cytochrome oxidase.

The principles for the operation of redox-linked proton pumps are reviewed and applied to one specific pump, cytochrome oxidase. Systematic studies of internal electron transfer in the different redox states of this pump will be facilitated by the development of methods for rapid electron injection into the metal centers of the enzyme. Two methods that have been employed to generate electron donors are pulse radiolysis and laser flash photolysis. The rate of electron injection from photoexcited Ru-modified cytochrome c or triplet Zn-cytochrome c into the CuA center is about 10(5) s-1, and the CuA/cytochrome a electron equilibration rate is 2 x 10(4) s-1. Electron transfer from cytochrome a to the cytochrome a3-CuB site occurs at 2 x 10(5) s-1 in the half-reduced enzyme, whereas the rate is only 2 x 10(2) s-1 in the peroxide intermediate, despite a much higher driving force. It is likely that variations in distant electronic coupling attributable to a ligand shuttle, as well as changes in the reorganization energy of one or more of the redox centers, contribute to the control of internal electron flow in the enzyme.

Amino Acid Sequence↗
PubMed1992

The simultaneous measurement of the redox state of cytochrome oxidase in heart and brain of rat in vivo by NIR.

The mutual relationship of the redox state of cytochrome oxidase in both cardiac and brain tissues were examined by the simultaneous optical measurement. The oxygenation states of cardiac and brain tissues behaved in a same manner during progressive hypoxia. We concluded that the oxygenation state of brain completely depends on the oxygenation state of cardiac tissue which determines the cardiac output.

Animals↗
PubMed1995

Contrast sensitivity and spatial frequency response of primate cortical neurons in and around the cytochrome oxidase blobs.

The striate cortex of macaque monkeys contains an array of patches which stain heavily for the enzyme cytochrome oxidase (CO blobs). Cells inside and outside these blobs are often described as belonging to two distinct populations or streams. In order to better understand the function of the CO blobs, we measured the contrast sensitivity and spatial frequency response of single neurons in and around the CO blobs. Density profiles of each blob were assessed using a new quantitative method, and correlations of local CO density with the physiology were noted. We found that the CO density dropped off gradually with distance from blob centers: in a typical blob the CO density dropped from 75% to 25% over 100 microns. Recordings were confined to cortical layers 2/3. Most neurons in these layers have poor contrast sensitivity, similar to that of the parvocellular neurons in the lateral geniculate nucleus. However, in a small proportion of layers 2/3 neurons we found higher contrast sensitivity, similar to that of the magnocellular neurons. These neurons were found to cluster near blob centers. This finding is consistent with (indirect) parvocellular input spread uniformly throughout layers 2/3, and (indirect) magnocellular input focused on CO blobs. We also measured spatial tuning curves for both single units and multiple unit activity. In agreement with other workers we found that the optimal spatial frequencies of cells near blob centers were low (median 2.8 c/deg), while the optimal frequencies of cells in the interblob regions were spread over a wide range of spatial frequencies. The high cut-off spatial frequency of multi-unit activity increased with distance from blob centers. We found no correlation between spatial bandwidth and distance from blob centers. All measured physiological properties varied gradually with distance from CO blob centers. This suggests that the view of blob cells subserving visual functions which are entirely distinct from non-blob cells may have to be reevaluated.

Animals↗
PubMed1990

The Pisum sativum mitochondrial gene encoding cytochrome oxidase subunit I has an unusual transcription pattern.

We report the transcriptional analysis of the mitochondrial (mt) gene encoding cytochrome oxidase subunit I (COXI). A probe made from the protein-coding region of the pea coxI gene hybridized to four RNA transcripts, two of which are much larger than necessary to encode the COXI polypeptide. The RNA hybridization was repeated with a series of sequential probes made from the 5'-untranslated region. The results of these experiments indicated that all four transcripts initiate between 2.8 and 2.1 kb upstream from the protein-coding region. Furthermore, the pattern of hybridization to these sequential probes was unusual, suggesting that introns are spliced out of the 5'-transcribed, but untranslated, region. A sequence located within one of the sequential probes is repeated elsewhere in the pea mt genome. Transcript termini were mapped for the 5' and 3' ends and putative regulatory sequences were located.

Base Sequence↗
PubMed1989

Analytical characterization of cytochrome oxidase preparations with regard to metal and phospholipid contents, peptide composition and catalytic activity.

A number of preparations of cytochrome oxidase have been analyzed for metals by energy dispersive X-ray fluorescence spectrometry. The EPR characteristics, the peptide compositions, the protein and phospholipid contents as well as the catalytic constants of the samples have also been determined. It is confirmed that the enzyme functional unit contains three copper atoms and one zinc atom in addition to two iron atoms. On the basis of the parameters determined for the different samples it is suggested that a high catalytic activity of a preparation can be correlated to a number of other analytical characteristics.

Copper↗
PubMedDate not supplied

Rapid identification of ocular dominance columns in macaques using cytochrome oxidase, Zif268, and dark-field microscopy.

Strabismus induces an abnormal pattern of alternating light and dark columns of cytochrome oxidase (CO) activity in macaque striate cortex. This pattern may arise because visual perception is suppressed in one eye to avoid diplopia. To test whether CO activity is reduced in the ocular dominance columns of the suppressed eye, we performed monocular enucleation to co-label the ocular dominance columns with Zif268 immunohistochemistry in seven exotropic adult Macaca fascicularis. This approach was unsuccessful, for two reasons. First, Zif268 yielded inconsistent labelling, that was usually greater in the enucleated eye's ocular dominance columns, but was sometimes greater in the intact eye's columns. Therefore, Zif268 was not a reliable method for identifying the ocular dominance columns serving each eye. Second, in three control animals we found that a brief survival period following monocular enucleation (needed for Zif268 levels to change) was long enough to alter CO staining. For example, a survival time of only 3 h was sufficient to induce CO columns, indicating that the activity of this enzyme fluctuates more rapidly than realized previously. Independent of these findings, we have also discovered that acute monocular enucleation produces a vivid pattern of ocular dominance columns visible in unstained or CO-stained sections under dark-field illumination. The ocular dominance columns of the acutely enucleated eye appear dark. This was verified by labelling the ocular dominance columns with [3H]proline. Dark-field illumination of the cortex after acute monocular enucleation offers a new, easy method for identifying the ocular dominance columns in macaques.

Animals↗
PubMed1984

Cytochrome oxidase subunit II gene of rice has an insertion sequence within the intron.

We have isolated and sequenced the cytochrome oxidase subunit II gene from rice (Oryza sativa L. var Labelle). The overall structural organization of this gene is very similar to that of the maize gene. This gene contains an intron in a position identical to the intron in the maize gene. However, the intron in the rice gene is longer than that of the maize gene largely due to a 461 bp insertion sequence, which has inverted repeats at its termini and is flanked by direct repeats, characteristic of transposable elements. Apart from this insertion sequence, the remainder of the intron sequence is strikingly homologous to that of maize (98.6% homology), suggesting a possible functional or structural role. The coding regions of the two genes exhibit 99.5% nucleotide sequence homology and their deduced amino acid sequences are identical. Similarly, the 3'-noncoding regions, except for several small insertions and deletions, show complete sequence homology. On the contrary, no sequence homology is detected in the 5'-noncoding regions.

Base Sequence↗
PubMed1982

Cytochrome oxidase subunit III gene in Neurospora crassa mitochondria. Location and sequence.

We have located and sequenced the gene for cytochrome oxidase subunit III (CoIII) in Neurospora crassa mitochondria. The CoIII gene is located downstream from the small rRNA gene within a cluster of tRNA genes and is coded by the same strand as the tRNA and the rRNA genes. Like the tRNA and the rRNA genes, the CoIII gene is also flanked by the GC-rich palindromic DNA sequences which are highly conserved in N. crassa mitochondria. The CoIII coding sequence predicts a protein 269 amino acids long including 8 tryptophan residues. All 8 tryptophan residues are coded for by UGA. This supports our previous conclusion based on the anticodon sequence of N. crassa mitochondrial tryptophan tRNA and provides evidence for the notion that use of UGA as a codon for tryptophan rather than chain termination may be a feature common to most mitochondrial protein synthesis systems. The close correspondence between the amino acid composition of N. crassa CoIII and that of the protein predicted by the CoIII gene sequence suggests that unlike in mammalian mitochondria, AUA is a codon for isoleucine and not for methionine in N. crassa mitochondria. The N. crassa CoIII sequence shows strong homologies to the corresponding yeast and human proteins (53 and 47%, respectively). The overall hydrophobic character of the protein is consistent with suggestions that most of CoIII is embedded in the mitochondrial inner membrane.

Amino Acid Sequence↗
PubMed1983

Alternative hypotheses of proton ejection in cytochrome oxidase vesicles. Transmembrane proton pumping or redox-linked deprotonation of phospholipid-cytochrome c complex(es).

A review of published experimental and interpretative knowledge concerning proton ejection associated with cytochrome c oxidation by artificial phospholipid vesicles inlaid with cytochrome c oxidase indicates that the detailed characteristics of the redox-linked proton ejection cannot be simply explained by proton pumping. We propose an alternative hypothesis according to which proton ejection is due to the redox-linked deprotonation of a complex involving phospholipid and cytochrome c at the surface of the vesicles. The postulates upon which this hypothesis depends are explicitly outlined, and some methods of testing the hypothesis are suggested.

Carbonyl Cyanide m-Chlorophenyl Hydrazone↗