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PubMed1992

Evolution of the mitochondrial cytochrome oxidase II gene among 10 orders of insects.

We examine the complete nucleotide sequences of the mitochondrial cytochrome oxidase II gene of 13 species of insects, representing 10 orders. The genes range from 673 to 690 bp in length, encoding 226 to 229 amino acids. Several insertion or deletion events, each involving one or two codons, can be observed. The 3' end of the gene is extremely variable in both length and sequence, making alignment of the ends unreliable. Using the first 639 nucleotide positions, for which unambiguous alignments could be obtained, we examine the neighbor-joining trees based on nucleotide divergences and based on conserved subsets of that data, including transversion and amino acid and second codon position divergences. Each of these subsets produces different trees, none of which can be easily reconciled with trees constructed using morphology and the fossil record. Bootstrap analysis using second codon positions strongly supports affinities between the order Blatteria (cockroaches) and the order Isoptera (termites) and between a wasp and the published honeybee sequence (Order Hymenoptera). The divergence of insect orders is very ancient and may have occurred too rapidly for easy resolution using mitochondrial protein sequences. Unambiguous resolution of insect orders will probably require analysis of many additional taxa, using the COII gene and other conserved sequences.

Amino Acid Sequence↗
PubMed1976

Low-temperature studies on mixed-valence cytochrome oxidase by using magnetic circular dichroism.

The spin states of the haem components of mixed-valence cytochrome oxidase were studied at room temperature and at temperature down to 20K by using magnetic circular dichroism. The room-temperature studies show the presence of a low-spin ferrous haem together with a low-spin ferric haem, which we attribute to heams a3 and a respectively. At temperatures below 100K it appears that the CO of the mixed-valence CO complex may be irreversibly photolysed, and that in this case haems a and a3 assume their high-spin states. Thus in this enzyme haem-haem interactions appear possible at temperatures below 100K.

Carbon Monoxide↗
PubMed2004

Cytochrome oxidase activity in hippocampal synaptic mitochondria during aging: a quantitative cytochemical investigation.

Synaptic mitochondria, cytochemically positive to cytochrome oxidase (COX) activity, were investigated by morphometric methods in the hippocampal dentate gyrus of adult and old rats. The number of mitochondria/microm(3) of tissue (Nv), the volume fraction occupied by mitochondria/microm(3) of tissue (Vv), the average mitochondrial volume (V), the longer mitochondrial diameter (F(max)), and the ratio R:mitochondrial area/overall area of the cytochemical precipitate due to COX activity were measured on COX-positive organelles. In old animals, Nv, Vv, V, and F(max) increased at a not significant extent; R was not significantly decreased. The complement (%) of longer organelles was higher in old animals. COX activity is currently considered an endogenous marker of neuronal oxidative metabolism; thus, although our findings refer to the discrete subpopulation of COX-positive organelles located at synaptic terminals, they support that changes of mitochondrial ultrastructure and metabolic competence may contribute to the age-related alterations of neuronal performances.

Aging↗
PubMed2002

Nitric oxide and cytochrome oxidase: substrate, inhibitor or effector?

Endogenously produced nitric oxide (NO) controls oxygen consumption by inhibiting cytochrome c oxidase, the terminal electron acceptor of the mitochondrial electron transport chain. The oxygen-binding site of the enzyme is an iron/copper (haem a3/CuB) binuclear centre. At high substrate (ferrocytochrome c) concentrations, NO binds reversibly to the reduced iron in competition with oxygen. At low substrate concentrations, NO binds to the oxidized copper. Inhibition at the haem iron site is relieved by dissociation of the NO from the reduced iron. Inhibition at the copper site is relieved by oxidation of the bound NO and subsequent dissociation of nitrite from the enzyme. Therefore, NO can be a substrate, inhibitor or effector of cytochrome oxidase, depending on cellular conditions.

Electron Transport Complex IV↗
PubMed2006

Molecular evolution at the cytochrome oxidase subunit 2 gene among divergent populations of the intertidal copepod, Tigriopus californicus.

The cytochrome c oxidase subunit 2 gene (COII) encodes a highly conserved protein that is directly responsible for the initial transfer of electrons from cytochrome c to cytochrome c oxidase (COX) crucial to the production of ATP during cellular respiration. Despite its integral role in electron transport, we have observed extensive intraspecific nucleotide and amino acid variation among 26 full-length COII sequences sampled from seven populations of the marine copepod, Tigriopus californicus. Although intrapopulation divergence was virtually nonexistent, interpopulation divergence at the COII locus was nearly 20% at the nucleotide level, including 38 nonsynonymous substitutions. Given the high degree of interaction between the cytochrome c oxidase subunit 2 protein (COX2) and the nuclear-encoded subunits of COX and cytochrome c (CYC), we hypothesized that some codons in the COII gene are likely to be under positive selection in order to compensate for amino acid substitutions in other subunits. Estimates of the ratio of nonsynonymous to synonymous substitution (omega), obtained using a series of maximum likelihood models of codon substitution, indicated that the majority of codons in T. californicus COII are under strong purifying selection (omega << 1), while approximately 4% of the sites in this gene appear to evolve under relaxed selective constraint (omega = 1). A branch-site maximum likelihood model identified three sites that may have experienced positive selection within the central California sequence clade in our COII phylogeny; these results are consistent with previous studies showing functional and fitness consequences among interpopulation hybrids between central and northern California populations.

Amino Acid Sequence↗
PubMed1979

The reaction of cytochrome oxidase with oxygen in the fission yeast Schizosaccharomyces pombe 972h-. Studies at subzero temperatures and measurement of apparent oxygen affinity.

1. Cytochrome alpha 3 in whole-cell suspensions of the fission yeast Schizosaccharomyces pombe reacted in the reduced form with CO to give a photodissociable CO complex with absorption maxima at 429, 543 and 591 nm in CO-liganded reduced-minus-reduced difference spectra. 2. Other CO-bound haemoproteins, cytochromes P-420 and P-450, were not photodissociated under the conditions employed. 3. Measurements of the rates of reassociation of CO with cytochrome alpha 3 after flash photolysis over the temperature range from -101 to -109 degrees C gave a value for Eact. of 28.6 kJ/mol. 4. Between -94 and -106 degrees C, O2 reacted with cytochrome oxidase in intact cells to give an oxygenated intermediate (compound A). 5. At -70 degrees C compound A was converted into a second spectrally distinct intermediate (compound B). 6. Electron transport, indicated by the oxidation of cytochromes alpha + alpha 3 and cytochrome c, did not occur until the temperature was raised to -50 degrees C. 7. At room temperature cytochfome oxidase was oxidized to 50% of its steady-state concentration by 0.35 microM-O2.

Ascomycota↗
PubMed1985

Distance between the visible copper and cytochrome a in bovine heart cytochrome oxidase.

Electron paramagnetic resonance (EPR) at 15 K was used to probe the magnetic interaction between the visible copper CuA2+ and ferric cytochrome a in the carbon monoxide compound of beef heart cytochrome oxidase. At pH 8.6, the midpoint potentials (Em's) for one-electron oxidation of CuA+ and cytochrome a2+ were found to be 195 and 235 mV, respectively. Because the Em of CuA is well below that of cytochrome a under these conditions, the microwave power saturation of CuA could be measured as a function of percentage cytochrome a oxidized. Although progressive power saturation data directly provide only the product of the spin-lattice and transverse relaxation rates delta [1/(T1T2)], Castner's theory for the saturation of inhomogeneously broadened lines [Castner, T.G., Jr. (1959) Phys. Rev. 115 (6), 1506-1515], along with our own theoretical formulation of the dipolar T2, enabled us to determine the change in T1 of CuA due to dipolar relaxation by cytochrome a. The orientation of the principal g values of CuA with respect to those of cytochrome a was evaluated in partially oriented membranous multilayers. When allowance was made for uncertainties in the relative CuA-cytochrome a configuration and in the dipolar axis-magnetic field orientation, a range for the spin-spin distance r was calculated on the basis of the dipolar T1 of the gx component of CuA. This distance range was further restricted by consideration of T1 for the nonunique orientations of CuA giving rise to the gy signal. Only those values of r are possible for which the calculated T1 ratio (gx/gy) is equal to the experimentally determined ratio.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Distribution of cytochrome oxidase in layers IV and V of the striate cortex in neonate monkeys.

The uniformly dense staining for cytochrome oxidase (CO) in layer IV of area 17 in adult monkeys has been described as developing from a bilaminar pattern in neonates being composed of a broad CO band in layer IV alpha and a narrow CO band attributed to the innermost zone of layer IV beta. Here we present evidence, in the neonate marmoset monkey, for the narrow CO band to be localized in the outermost rim of layer V, designated as sublayer Va.

Aging↗
PubMed1980

Small-angle X-ray scattering studies of oxidized and reduced cytochrome oxidase from Pseudomonas aeruginosa.

Small-angle X-rays scattering experiments were performed with oxidized and reduced cytochrome oxidase purified from Pseudomonas aeruginosa. The radii of gyration were calculated to be 40.5 A for the oxidized form and 37.0 A for the reduced. The longest dimension of the oxidized enzyme was 120 A while for the reduced it was 100 A. The volume of the oxidized protein was observed to be slightly greater than that of the reduced. These data indicate that there is a contraction of the structure of the enzyme during reduction of its constituent heme groups.

Electron Transport Complex IV↗
PubMed1993

Brain cytochrome oxidase activity after kindled seizures: a quantitative histochemical mapping study.

Quantitative histochemistry was used to analyze changes in cytochrome oxidase (CO) activity in 93 brain regions after entorhinal cortex kindling. Rats were kindled to at least six stage-5 seizures and sacrificed either 24 h or 28 days after the last convulsion. Regional brain CO activity was quantitated in histological sections using calibrated densitometric standards. No statistically significant differences in regional CO activity between kindled and control brains were seen either 24 h or 28 days after the last convulsion. These results suggest that the brain changes underlying the kindling state are not reflected in localized alterations in mitochondrial respiratory capacity. They also indicate that long-lasting changes in regional brain CO activity recently found after electroconvulsive shock are not common to all types of seizures.

Animals↗
PubMed1993

Sequence of the mitochondrial gene encoding subunit I of cytochrome oxidase in Saccharomyces douglasii.

We have determined the complete sequence of the mitochondrial (mt) gene (COXI) coding for cytochrome oxidase subunit I of Saccharomyces douglasii. This gene is 7238 bp long and includes four introns. The salient feature of the S. douglasii COXI gene is the presence of two introns, Sd.ai1 and Sd.ai2, which have not been observed in S. cerevisiae genes. Both are group-I introns and are located at novel positions compared with the S. cerevisiae COXI. Interestingly, one of these introns (the second one) is inserted at the same position as intron 2 of COXI of Kluyveromyces lactis and also as intron 8 of the same gene in Podospora anserina. The ORFs contained in these three introns display a high degree of similarity. Comparisons of exonic and intronic sequences of the COXI of two Saccharomyces species reinforces our previous conclusions: the evolution of mt genes in yeast obeys different rules to those found in vertebrates.

Amino Acid Sequence↗
PubMed2000

Proton pumping by cytochrome oxidase: progress, problems and postulates.

The current status of our knowledge about the mechanism of proton pumping by cytochrome oxidase is discussed. Significant progress has resulted from the study of site-directed mutants within the proton-conducting pathways of the bacterial oxidases. There appear to be two channels to facilitate proton translocation within the enzyme and they are important at different parts of the catalytic cycle. The use of hydrogen peroxide as an alternative substrate provides a very useful experimental tool to explore the enzymology of this system, and insights gained from this approach are described. Proton transfer is coupled to and appears to regulate the rate of electron transfer steps during turnover. It is proposed that the initial step in the reaction involves a proton transfer to the active site that is important to convert metal-ligated hydroxide to water, which can more rapidly dissociate from the metals and allow the reaction with dioxygen which, we propose, can bind the one-electron reduced heme-copper center. Coordinated movement of protons and electrons over both short and long distances within the enzyme appear to be important at different parts of the catalytic cycle. During the initial reduction of dioxygen, direct hydrogen transfer to form a tyrosyl radical at the active site seems likely. Subsequent steps can be effectively blocked by mutation of a residue at the surface of the protein, apparently preventing the entry of protons.

Animals↗
PubMed1997

Quantitative cytochemistry of cytochrome oxidase and cellular morphometry of the human inferior colliculus in control and Alzheimer's patients.

Quantitative cytochemistry of cytochrome oxidase (C.O.) was implemented in human brains to measure C.O. activity in the 3 main divisions of the inferior colliculus (IC): central (ICC), dorsal (ICD), and external (ICE). Units of C.O. activity (micromol/min/g tissue wet weight) were quantified in cellular compartments (overall average, neuropil, perikaryon, and dendrites) at the light microscope level using microdensitometry calibrated with C.O. activity standards measured spectrophotometrically. In a non-AD (Alzheimer's disease) control group (mean age = 79.6 +/- 3.1 years, postmortem time = 6.9 +/- 1.6 h), the ICC and ICD demonstrated higher (p < 0.008) overall average activities (mean = 183.40 +/- 18.7 and 184.98 +/- 45.1 units, respectively) relative to the ICE (56.46 +/- 15.9 units). Comparison of cellular morphometry (soma and nucleus area, perimeter, and diameter) revealed that the ICC contained cells of significantly larger soma size than in both the ICD and ICE (p < 0.002). The distribution of soma diameters in the ICC of controls showed a clear bimodality, enabling the typing of the cells into larger and smaller than average soma diameter. Brains from patients with Alzheimer's disease (AD; mean age = 78.3 +/- 2.9 years, postmortem time = 6.5 +/- 1.3 h) were compared with the non-AD controls. Significant group differences were found only in the large cells of the ICC. The AD large cells showed a decrement in C.O. activity relative to the corresponding controls in overall average activity (p < 0.032) and in peak activity of neuropil near the soma (p < 0.012). These findings provide the first quantitative cytochemical data of C.O. activity in humans. They also suggest that cellular alterations in C.O. metabolism in AD affect predominantly specific groups of larger projection neurons while neighboring neurons are spared.

Aged↗
PubMed1990

Effects of monocular enucleation, tetrodotoxin, and lid suture on cytochrome-oxidase reactivity in supragranular puffs of adult macaque striate cortex.

The laminar structure and cellular distribution of cytochrome-oxidase (CO) reactivity in supragranular puffs of striate cortex was examined in adult macaque monkeys surviving various periods of monocular enucleation, lid suture, and retinal impulse blockage with tetrodotoxin (TTX). Enucleation and TTX produced a rapid and severe loss in the size of the CO reactive region in puffs dominated by the removed or treated eye compared to slower and less marked reductions obtained in deprived puffs of lid-sutured monkeys. In all deprived animals, the cross-sectional areas of deprived puffs decreased most rapidly in the upper layers (2 and 3A). In long-term enucleated (60 wks) and TTX-treated (4 wks) monkeys, puff area was severely reduced in layer 3B, while reactivity in layer 3B appeared partially spared in lid-sutured monkeys. The density of the CO reaction product was significantly and evenly reduced throughout deprived puffs for all of the monkeys examined; however, this decrease was less severe in adult monkeys lid-sutured for 11 wks. Although no evidence for cell loss was obtained, all three forms of visual deprivation led to lower counts of neuronal perikarya with high levels of CO reaction product in both deprived puff and interpuff areas. This effect was less marked in the deprived puffs of monkeys lid-sutured for 2.5 and 3 yrs, suggesting recovery of CO activity in some neurons. Neurons in deprived puffs and interpuffs were generally similar in size to those in nondeprived regions, although CO-reactive cells were significantly smaller in the deprived puffs of monkeys enucleated for 28.5 or 60 wks. These results indicate that the metabolic response of neuronal elements in supragranular striate cortex depends upon the nature of the visual deficit. The partial sparing of CO reactivity in deprived puffs of lid-sutured monkeys may reflect the continued transmission of certain types of visual stimuli through a closed eyelid.

Animals↗
PubMed2003

Distribution of non-phosphorylated neurofilament in squirrel monkey V1 is complementary to the pattern of cytochrome-oxidase blobs.

The geniculo-recipient zones of the primate primary visual cortex (V1) stain more strongly for cytochrome oxidase (CO) than other regions. Labeling V1 with an antibody (SMI-32) against neurofilament protein produces a laminar pattern that is largely complementary to that of CO: the layers that receive the strongest geniculate input react weakly for SMI-32. We evaluated whether the complementary laminar relationship extends throughout the superficial layers where there are regularly spaced blobs of dark CO staining that are known to receive geniculate input. In all hemispheres, neurofilament labeling in the superficial layers was indeed complementary to the CO pattern. The density of SMI-32 labeled neurons was quantified and found to be greater within the CO interblobs than in the blobs. These results demonstrate that blobs and interblobs can be distinguished by examining the pattern of neurofilament expression in V1. That neurofilament expression is highest within interblobs raises the possibility that the distribution of cell types may be non-uniform across blobs and interblobs.

Animals↗
PubMedDate not supplied

The global pattern of cytochrome oxidase stripes in visual area V2 of the macaque monkey.

In primate visual area V2, histochemical staining for cytochrome oxidase (CO) reveals a tripartite pattern of densely labeled thick and thin stripes separated by pale interstripes. This modularity is believed to be related to functionally distinct processing streams that course through the hierarchy of visual areas. Here, we studied the overall pattern of CO stripes in V2 of the macaque monkey, using tissue that had been physically unfolded and flattened prior to histological sectioning. CO stripes were identified on the basis of their physical dimensions and on their differential immunoreactivity for the monoclonal antibody Cat-301. We observed several distinctive features of compartmental organization in V2. The most prominent was a dorso-ventral asymmetry in the stripe pattern, occurring in the majority of cases studied. In dorsal V2, most stripes measure approximately 10 mm in length and run roughly orthogonal to both the posterior and anterior borders of V2. In contrast, many stripes in ventral V2 have a curved or oblique trajectory, and some extend up to 20 mm in length. Stripes following a curved trajectory often become nearly parallel to the anterior border of V2. These differences imply an asymmetry in how the visual field maps onto dorsal versus ventral stripes. Occasionally, thin stripes fail to alternate with thick stripes but instead occur next to one other, separated only by interstripes. In three most complete reconstructions, we found that unfolded V2 is approximately 110 mm in length, approximately 900 mm2 in surface area, and that it contains approximately 28 complete sets of stripes (one thick, one thin and two interstripes), yielding an average of approximately 4 mm per set of stripes. The maximum width of ventral V2 (13-14 mm) exceeds that of dorsal V2 (10 mm), and there is a consistent narrowing of V2 in the region of foveal representation (3-5 mm).

Animals↗