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PubMed2000

Hierarchy within human SI: supporting data from cytochrome oxidase, acetylcholinesterase and NADPH-diaphorase staining patterns.

The human primary somatosensory cortex consists of four cytoarchitectonic subdivisions (3a, 3b, 1 and 2) that are likely to contain distinct somatosensory representations. The intraareal organization of these areas as well as that of the primary motor cortex (area 4) has been analyzed using histochemical stains of cytochrome oxidase, acetylcholinesterase and NADPH-diaphorase activity in normal human brains. Cytochrome oxidase activity was revealed in individual cortical neurons and neuropil. Areas 4, 3a and 3b were on average darker than areas 1 and 2. The laminar distribution of cytochrome oxidase activity varied in different areas. A prominent dark band was present in layers IV and lower III in areas 3a and 3b and in layer III in areas 1, 2 and 4. Acetylcholinesterase staining revealed fibers and pyramidal cells in layers III and V; stained layer III pyramids were rare in areas 3a and 3b and numerous in areas 1, 2 and 4. NADPH-diaphorase positive elements included Golgi-like stained non-pyramidal neurons and Nissl-like stained pyramidal neurons; the former were found, in small numbers, in layer II of areas 4, 3a, 3b and 1, and the latter in layers III and V of areas 4 and 3a and in layer V of areas 1 and 2. The dark cytochrome oxidase staining of layer IV and the paucity of acetylcholinesterase positive pyramids in areas 3a and 3b resemble the pattern found in primary visual and auditory areas, whereas the dark cytochrome oxidase staining in layer III and abundance of acetylcholinesterase positive pyramids in areas 1 and 2 that of association areas. These results suggest that the four areas included in human SI constitute hierarchical stages of cortical processing, with 3a and 3b corresponding to primary and 1 and 2 to secondary areas.

Acetylcholinesterase↗
PubMed1967

Ultrastructural demonstration of cytochrome oxidase activity by the Nadi reaction with osmiophilic reagents.

A new method for the subcellular and cytochemical demonstration of cytochrome oxidase has been developed with the introduction of N-benzyl-p-phenylenediamine (BPDA) and the discovery that indoanilines are osmiophilic. These indoanilines produced upon oxidation of BPDA in the presence of naphthols are highly colored compounds that yield electron-opaque coordination polymers of osmium (osmium black) that are amorphous, insoluble in water, and in organic solvents. The best methods for preparing rat tissue were in decreasing order: fixation in formaldehyde solution, fresh tissue slices, and frozen sections of fresh or fixed tissue. Ultrathin sections were counterstained by bridging with the thiocarbohydrazide-osmium tetroxide (T-O) procedure for enhancing underlying membranous structures. Cytochrome oxidase activity was noted primarily in mitochondria and occasionally in sarcotubules of heart, in mitochondria and occasionally in infoldings of the plasma membrane of renal tubular cells, and in mitochondria and, to a great extent, in endoplasmic reticulum of hepatic cells. Cytochrome oxidase activity produced deposits in droplet form, whereas dehydrogenase activity resulted in uniform staining of mitochondrial cristae, as recently demonstrated with an osmiophilic tetrazolium salt. Even more recently we have succeeded in demonstrating cytochrome oxidase activity in nondroplet staining on mitochondrial cristae with an osmiophilic benzidine-type reagent that apparently polymerizes upon oxidation (to be published later).

Amines↗
PubMed1987

Spin-label studies on the specificity of interaction of cardiolipin with beef heart cytochrome oxidase.

The selectivity of interaction of various cardiolipin analogues with beef heart cytochrome oxidase in reconstituted complexes with dimyristoylphosphatidylcholine has been studied by electron spin resonance spectroscopy, using lipids spin-labeled in the acyl chains. No difference in selectivity is observed between cardiolipin and its monolyso derivative, and similarly no selectivity is observed between phosphatidylcholine and lysophosphatidylcholine. Removal of the cardiolipin charge by methylation of the phosphate groups reduces but does not eliminate selectivity relative to phosphatidylcholine. The dependence of the lipid selectivity on head group and chain composition is in the order cardiolipin approximately equal to monolysocardiolipin greater than acylcardiolipin greater than dimethylcardiolipin greater than phosphatidylcholine approximately equal to lysophosphatidylcholine, where acylcardiolipin has the spin-label chain attached at the center -OH of the head group. The degree of association of the negatively charged cardiolipin derivatives with cytochrome oxidase decreases with increasing salt concentration, to a level comparable to that for dimethylcardiolipin. At high ionic strength there is still a marked selectivity relative to phosphatidylcholine. Li+ ions are more effective in screening the interaction than are Na+ ions, and divalent ions are more effective than monovalent ions. The selectivity for cardiolipin is only slightly reduced on titrating the protein to high pH. Alkylation of the protein with N-ethylmaleimide has little effect on the titration behavior. Covalent modification of the protein by reaction with citraconic anhydride decreases the selectivity of interaction with cardiolipin. It is concluded that cardiolipin possesses an additional specificity of interaction with cytochrome oxidase other than that of purely electrostatic origin.

Animals↗
PubMed1990

Identification of a periplasmic C-type cytochrome as electron donor to the plasma membrane-bound cytochrome oxidase of the cyanobacterium Nostoc Mac.

Photoautotrophically grown cyanobacterium Nostoc sp. strain Mac (PCC 8009) released up to about 10 nmol of a c-type cytochrome per ml packed cells after treatment with EDTA under conditions that left the plasma membrane absolutely intact as judged from the absence of cytosolic proteins in the supernatant. Spectra of the ascorbate reduced cytochrome revealed peaks at 553, 522 and 416 nm. The protein was purified to an A-553/A-275 ratio of 0.8. Midpoint potential (at pH 7), isoelectric point and apparent molecular weight of the cytochrome were +0.35 V, 8.6, and around 10,500, respectively. The cytochrome proved to be an excellent electron donor to the aa3-type cytochrome oxidase in both plasma and thylakoid membranes isolated and purified from Nostoc Mac. Chemoheterotrophic growth of the cells increased the level of periplasmic cytochrome c up to 10-fold and cytochrome oxidase activity of plasma membranes up to 90-fold. The periplasmic cytochrome also transferred electrons to photosystem I in illuminated thylakoid membranes. We conclude that cyanobacteria contain a periplasmic c-type cytochrome presumably identical to so-called cytochrome c6 or c-553 which has long been known as a photosynthetic (i.e. thylakoid-associated) redox protein in these organisms, and which is capable of donating electrons (from the periplasmic space) to the cytochrome oxidase in the plasma membrane and (from the thylakoid lumen) to both P700 and cytochrome oxidase in the thylakoid membrane.

Cell Membrane↗
PubMed1977

On the reaction of cyanide with an oxygenated form of cytochrome oxidase.

The reaction of an oxygenated form of cytochrome oxidase [EC 1.9.3.1] with cyanide was examined under conditions where spontaneous decay was prevented. The equilibrium and kinetic constants for the reaction agreed well with those for the normally operating enzyme, indicating that the oxygenated form is one of the active intermediates of the cytochrome oxidase reaction.

Animals↗
PubMed1985

Effect of administration of 2-methyl-4-dimethylaminoazobenzene on the half-lives of rat liver mitochondria and cytochrome oxidase.

The turnover of total mitochondrial proteins and cytochrome oxidase in the livers of rats administered with 2-methyl-4-dimethylaminoazobenzene (2-Me-DAB) has been determined. The incorporation of [14C]bicarbonate revealed a half-life of 3.1 days in control and 6 to 9 days in azodye administered animals for whole mitochondrial proteins. The incorporation of [35S]methionine yielded t1/2 values of 8.5 days and 15.4 days, respectively. The t1/2 of cytochrome oxidase, 10.8 days for control and 19.3 days for 2-Me-DAB-treated animals, indicated that the delay in the decay of the enzyme was of the same order as that of whole mitochondria. Short term incorporation revealed that the administration of the azodye stimulated the synthesis of the enzyme. Mitochondria isolated from azodye-administered animals appeared less susceptible to lysosomal proteolysis. Also, azodye administration seemed to impair the ability of lysosomes to degrade mitochondria.

Animals↗
PubMed1996

Characterization of COX17, a yeast gene involved in copper metabolism and assembly of cytochrome oxidase.

Mutations in the COX17 gene of Saccharomyces cerevisiae cause a respiratory deficiency due to a block in the production of a functional cytochrome oxidase complex. Because cox17 mutants are able to express both the mitochondrially and nuclearly encoded subunits of cytochrome oxidase, the Cox17p most likely affects some late posttranslational step of the assembly pathway. A fragment of yeast nuclear DNA capable of complementing the mutation has been cloned by transformation of the cox17 mutant with a library of genomic DNA. Subcloning and sequencing of the COX17 gene revealed that it codes for a cysteine-rich protein with a molecular weight of 8,057. Unlike other previously described accessory factors involved in cytochrome oxidase assembly, all of which are components of mitochondria, Cox17p is a cytoplasmic protein. The cytoplasmic location of Cox17p suggested that it might have a function in delivery of a prosthetic group to the holoenzyme. A requirement of Cox17p in providing the copper prosthetic group of cytochrome oxidase is supported by the finding that a cox17 null mutant is rescued by the addition of copper to the growth medium. Evidence is presented indicating that Cox17p is not involved in general copper metabolism in yeast but rather has a more specific function in the delivery of copper to mitochondria.

Amino Acid Sequence↗
PubMed2000

Regional brain variations of cytochrome oxidase activity and motor co-ordination in staggerer mutant mice.

A mutant mouse with cerebellar cortical atrophy, staggerer, was examined in tests of motor activity and co-ordination as well as in regional brain metabolism as assessed by cytochrome oxidase activity. Compared with non-ataxic controls, staggerer mutants had inferior performances in the open field, the wooden beam, the wooden edge, and the rotorod tests. An increase in cytochrome oxidase activity in the deep cerebellar nuclei and in some cerebellar efferent regions, such as the lateral vestibular nucleus, the parvicellular red nucleus, and the ventral tegmental area, was found in staggerer mutant mice. Abnormally high cytochrome oxidase activity in the interpositus and the dentate nuclei was linearly correlated with poor performance on the wooden beam and on the rotorod. High cytochrome oxidase activity in the lateral vestibular nucleus was also associated with poor performance on the wooden beam. Moreover, high cytochrome oxidase activity in the fastigial nucleus was associated with poor performance on the wooden beam but with high motor activity in the open field. These results indicate that a lack of innervation of Purkinje cells to the deep cerebellar nuclei is in part the cause of motor co-ordination deficits in staggerer mutant mice.

Animals↗
PubMed1953

Cytochrome oxidase activity during diapause and metamorphosis of the Japanese beetle, Popillia japonica Newman.

1. Determinations were made on the activity of cytochrome oxidase of individual Japanese beetles during growth, diapause, and metamorphosis. All readings were made on homogenates at a dilution of 1:1,000, except for adult beetles, when the final dilution was 1:10,000. 2. The activity of the enzyme increased during larval growth from a low value of 0.022 in the second instar, to high values ranging from 0.074 to 0.083 in diapause third instar larvae. 3. The high activity of cytochrome oxidase during larval diapause indicates that this condition may be physiologically different from that occurring in the egg or pupal stages of most other insects. 4. During metamorphosis, the activity of cytochrome oxidase follows the characteristic U-shaped curve associated with respiratory metabolism. It thus appears that most of the oxidation occurring in metamorphosing individuals is mediated through the cytochrome system. 5. The activity of cytochrome oxidase is significantly higher in the adult male than it is in the adult female; the values (calculated on the basis of a 1:1,000 dilution) were 0.40 +/- 0.028 and 0.25 +/- 0.012, respectively.

Animals↗
PubMed1984

Effects of oxygen on the antagonism of cyanide intoxication: cytochrome oxidase, in vitro.

Since oxygen was reported to be an effective cyanide antagonist in vivo, particularly in the presence of the classic antidotal combination of sodium nitrite and sodium thiosulfate, in vitro studies were initiated in an attempt to investigate the mechanism of oxygen-mediated cyanide antagonism. The effect of oxygen on cyanide-inhibited cytochrome oxidase with and without cyanide antagonist(s) was investigated in a purified membraneous enzyme system prepared from rat liver mitochondria. Cyanide produced a concentration dependent inhibition of cytochrome oxidase, and 100% oxygen did not alter the inhibition produced by KCN either in the presence or absence of sodium thiosulfate. However, the addition of sodium thiosulfate and rhodanese to the assay reactivated the cyanide-inhibited cytochrome oxidase. Kinetic analysis indicated rhodanese competes with cytochrome oxidase for cyanide, and oxygen had no effect on this coupled reaction. In conclusion, the in vivo antidotal properties of oxygen cannot be attributed to oxygen-mediated reactivation of cyanide-inhibited cytochrome oxidase or an oxygen-mediated acceleration of rhodanese detoxification.

Animals↗
PubMed1997

COX15 codes for a mitochondrial protein essential for the assembly of yeast cytochrome oxidase.

The respiratory defect of Saccharomyces cerevisiae mutants assigned to complementation group G4 of a pet strain collection stems from their failure to synthesize cytochrome oxidase. The mutations do not affect expression of either the mitochondrially or nuclearly encoded subunits of the enzyme. The cytochrome oxidase deficiency also does not appear to be related to mitochondrial copper metabolism or heme a biosynthesis. These data suggest that the mutants are likely to be impaired in assembly of the enzyme. A gene designated COX15 has been cloned by transformation of mutants from complementation group G4. This gene is identical to reading frame YER141w on chromosome 5. To facilitate further studies, Cox15p has been expressed as a biotinylated protein. Biotinylated Cox15p fully restores cytochrome oxidase in cox15 mutants, indicating that the carboxyl-terminal sequence with biotin does not affect its function. Cox15p is a constituent of the mitochondrial inner membrane and, because of its resistance to proteolysis, probably is largely embedded in the phospholipid bilayer of the membrane. The present studies further emphasize the complexity of cytochrome oxidase assembly and report a new constituent of mitochondria involved in this process. The existence of COX15 homologs in Schizosaccharomyces pombe and Caenorhabditis elegans suggests that it may be widely distributed in eucaryotic organisms.

Amino Acid Sequence↗
PubMed2002

Nitric oxide does not inhibit cerebral cytochrome oxidase in vivo or in the reactive hyperemic phase after brief anoxia in the adult rat.

In this study, near-infrared spectroscopy was applied to examine whether cytochrome oxidase in the rat brain is inhibited by nitric oxide in vivo. During normoxia, intravenous N(G)-nitro-L-arginine methyl ester (L-NAME) administration significantly decreased the cerebral saturation of hemoglobin with oxygen but did not alter the cytochrome oxidase redox state. Anoxia significantly reduced the cytochrome oxidase. The time course of the recovery of the redox state during reoxygenation was not altered by L-NAME. The results suggest that in adult rats, cytochrome oxidase is not inhibited by nitric oxide, either in physiologic conditions or during reoxygenation after a brief anoxic period.

Animals↗
PubMed1991

Cytochrome oxidase genes from Thermus thermophilus. Nucleotide sequence and analysis of the deduced primary structure of subunit IIc of cytochrome caa3.

Cytochrome caa3, a cytochrome c oxidase from Thermus thermophilus, is a two-subunit enzyme containing the four canonical metal centers of cytochrome c oxidases (cytochromes a and a3; copper centers CuA and CuB) and an additional cytochrome c. The smaller subunit contains heme C and was termed the C-protein. We have cloned the genes encoding the subunits of the oxidase and determined the nucleotide sequence of the C-protein gene. The gene and deduced primary amino acid sequences establish that both the gene and the protein are fusions with a typical subunit II sequence and a characteristic cytochrome c sequence; we now call this subunit IIc. The protein thus appears to represent a covalent joining of substrate (cytochrome c) to its enzyme (cytochrome c oxidase). In common with other subunits II, subunit IIc contains two hydrophobic segments of amino acids near the amino terminus that probably form transmembrane helices. Variability analysis of the Thermus and other subunit II sequences suggests that the two putative transmembrane helices in subunit II may be located on the surface of the hydrophobic portion of the intact cytochrome oxidase protein complex. Also in common with other subunits II is a relatively hydrophilic intermembrane domain containing a set of conserved amino acids (2 cysteines and 2 histidines) which have previously been proposed by others to serve as ligands to the CuA center. We compared the subunit IIc sequence with that of related proteins. N2O reductase of Pseudomonas stutzeri, a multi-copper protein that appears to contain a CuA site (Scott, R.A., Zumft, W.G., Coyle, C.L., and Dooley, D.M. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 4082-4086), contains a 59-residue sequence element that is homologous to the "CuA sequence motif" found in cytochrome oxidase subunits II, including all four putative copper ligands. By contrast, subunit II of the Escherichia coli quinol oxidase, cytochrome bo, also contains a region homologous to the CuA motif, but it lacks the proposed metal binding histidine and cysteine residues; this is consistent with the apparent absence of CuA from cytochrome bo.

Amino Acid Sequence↗
PubMed1996

Regulation of cytochrome oxidase: theoretical studies.

Using the dynamic model of oxidative phosphorylation developed previously and tested for its validity under a broad range of conditions some properties of cytochrome oxidase in the whole system considered were simulated. The regulation of this enzyme by oxygen concentration, delta p and reduction level of cytochrome c were studied. Assuming at least qualitative validity of the model, the following conclusions were drawn: (1) Regulation of cytochrome oxidase is different under the same conditions, when changes in the system (oxidative phosphorylation in isolated mitochondria) are imposed by a decrease in oxygen concentration (aerobiosis-->anaerobiosis transition) or by addition of hexokinase (state 4-->state 3 transition). In the former case, cytochrome c and delta p play a very similar role in the compensation for a decrease in the respiration rate caused by lowered oxygen concentration, while in the latter case changes in delta p activate cytochrome oxidase much stronger than changes in the reduction level of cytochrome c. (2) There is no unique thermodynamic flux-force relationship for cytochrome oxidase. This relationship depends on how the thermodynamic span of the reaction catalyzed by this enzyme is changed (aerobiosis-->anaerobiosis transition vs. state 4-->state 3 transition). (3) Under some conditions (aerobiosis-->anaerobiosis transition) the flux-force relationship can be inverse, i.e. increase in a thermodynamic force occurs simultaneously with decrease in a reaction rate.

Aerobiosis↗
PubMed1998

No association between Alzheimer plaques and decreased levels of cytochrome oxidase subunit mRNA, a marker of neuronal energy metabolism.

It has been proposed that neuritic plaques or toxic substances diffusing from them contribute to neurodegeneration in Alzheimer disease. We examined this hypothesis by looking for evidence of decreased neuronal energy metabolism in the proximity of neuritic plaques. Levels of mitochondrial DNA-encoded mRNA for subunit III of cytochrome oxidase, a marker of neuronal energy metabolism, were determined in post mortem brain samples. Consistent with earlier results, overall cytochrome oxidase subunit III mRNA levels were decreased in Alzheimer midtemporal cortex compared with controls. However, this reduction did not correlate with plaque density. In Alzheimer brains, cytochrome oxidase subunit III mRNA levels in neurons bearing neurofibrillary tangles were lower than in tangle-free neurons. However, neuronal cell bodies in close proximity of neuritic plaques showed no decrease in cytochrome oxidase subunit III mRNA or total polyadenylated mRNA compared with more distant neurons. Cytochrome oxidase enzyme activity in neuronal processes also showed no local reduction around neuritic plaques. These results suggest that neuritic plaques do not contribute to reduced neuronal energy metabolism in Alzheimer disease.

Aged↗
PubMed1969

The re-distribution of cytochrome oxidase, noradrenaline and adenosine triphosphate in adrenergic nerves constricted at two points.

1. The experiments correlate certain changes in the ultrastructure of cat hypogastric nerves constricted at two points with the distribution of a mitochondrial enzyme (cytochrome oxidase), noradrenaline (stored in some of the vesicles with an electron dense core, i.e. granular vesicles) and adenosine triphosphate (ATP) (present in noradrenaline storage granules, mitochondria and the soluble fraction of the axon).2. Noradrenaline (NA) and granular vesicles accumulated proximal but not distal to both constrictions. The total amount of NA and the concentration of granular vesicles above the first constriction was greater than that present in a similar piece of normal nerve, indicating that the cell body was continuing to produce the transmitter despite injury to its axon. The granular vesicles proximal to the first constriction were found in swollen or distorted axons and in new axonal outgrowths. It was concluded that the movement of NA in these constricted nerves was only centrifugal in direction.3. Mitochondria and cytochrome oxidase accumulated on both sides of the two constrictions, indicating a bi-directional movement of mitochondria in the damaged axons. The possibility that some of the increase in the cytochrome oxidase could be related to an increase in the number of mitochondria in cells other than neurones is considered.4. The adenosine triphosphate content increased on both sides of the two constrictions. This increase developed more slowly and was less marked than that of the other two substances.5. It was concluded that (a) there was a close correlation between the behaviour of noradrenaline and granular vesicles and between cytochrome oxidase and mitochondria, (b) the dense cored vesicles and the mitochondria moved independently of one another and at different rates after constriction of non-myelinated axons, (c) while some of the changes may be attributed to an obstruction to the free movement of axoplasm others may be due to an active reaction to axonal injury, and (d) localized intraaxonal synthesis of noradrenaline and cytochrome oxidase did not occur between the two constrictions.

Adenosine Triphosphate↗