Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.9.3.1 (cytochrome oxidase)
 8,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cytochrome c1 forms an active complex with cytochrome c as previously reported (Chiang, Y. L., Kaminsky, L. S., and King, T. E. (1976) J. Biol. Chem. 251, 29-36). It also forms a complex with cytochrome oxidase with heme ratio of 1:1. This cytochrome c1.oxidase complex has been purified by ammonium sulfate fractionation and is stable in media of high ionic strength (greater than 0.1 M) but dissociates as the pH deviates from neutral. The purified cytochrome c1 aggregates to an oligomer, presumably a pentamer. No agent has been found to depolymerize isolated c1 without denaturation. However, in the cytochrome c1.oxidase complex, these two cytochromes apparently were depolymerized to form smaller aggregates, if not monomeric units, as judged by sedimentation behavior. Cytochrome c1 also forms a ternary complex with cytochrome c and oxidase in the heme ratio of 1:1:1. This complex can be prepared by any of the following four methods: (i) c1 + c + oxidase: (ii) c1.c complex + oxidase; (iii) c1 + c.oxidase complex: or (iv) c + c1.oxidase complex. The mode of formation of these complexes is all from pure protein-protein interactions. Cytochrome c1 is also incorporated into phospholipid vesicles and these vesicles show about 200 molecules of phospholipid/cytochrome c1 in terms of heme. The spectrophotometric, circular dichroic, sedimentation behavior and enzymic properties of these complexes have been investigated.
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PMID:Cytochrome c1 complexes. 3 86

The pH-induced dissociation of cytochrome c oxidase from dimer to protomer has been studied in the pH range 7 to 11. Findings are as follows: The heme A:copper ratio is 1.0 at both pH 7.4 and 10.6. The relative enzymatic activity is preserved at all pH values at which the dimer or protomer are found. The fraction of protomer, determined from sedimentation velocity profiles, increases from 0 to 1 as the pH is raised. The absorption and circular dichroism spectra in the Soret region change in ways indicating that the contributions of cytochrome a in typical cytochrome aa3 spectral patterns are progressively lost as pH increases. At pH values more alkaline than the above, denaturation occurs. The fraction of protomer, and certain parameters defined to quantitate the changes in spectral form, exhibit similar pH profiles for a given preparation; but these concerted changes occur over different pH ranges for different preparations. Nevertheless the optical parameters are linearly correlated with the fraction of protomer for each preparation. It is concluded that the spectral properties of the dimer and the protomer are intrinsic attributes of each species and are not directly affected by changes in ambient pH.
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PMID:Characterization of the pH-dependent dimer-to-protomer transformation of cytochrome C oxidase at alkaline pH. 4 Dec 75

Diaminobenzidine, DAB, was applied to segments of aerobically and anaerobically grown coleoptiles of rice, Oryza sativa L., with the object of studying the location of cytochrome oxidase at the electron-microscope level. A specific staining of mitochondrial cristae and inner membrane was obtained, with no reaction in other organelles; with extended periods of incubation, the reaction product filled the mitochondria completely. In anaerobically grown coleoptiles, the reaction was much slower and the difference was particularly marked in vascular bundle companion cells and parenchyma, which gave the strongest reaction in aerobic tissue, but in the anaerobic stained even less than the cortical parenchyma. The reaction was inhibited by boiling and slowed very much by lowering of the incubation temperature from 27 to 4 degrees C. This indicated the involvement of an enzymic reaction and cyanide inhibition indicated that a haem enzyme was involved. The catalase inhibitor aminotriazole did not inhibit DAB oxidation. Nevertheless the specificity of the reaction for cytochrome oxidase must be questioned, because preheating of the tissue to 60 degrees C before incubation, which would be expected to destroy cytochrome oxidase activity, failed to decrease the oxidation, at least in aerobically grown coleoptiles. It is concluded that DAB is oxidized in the rice coleoptile tissue by a cytochrome system, and the development of this system is inhibited by anaerobiosis, but the oxidation cannot be claimed to represent cytochrome oxidase activity exclusively. Perhaps other autoxidizable, more heat-stable cytochromes participate in the reaction.
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PMID:The reaction of mitochondria in the coleoptiles of rice (Oryza sativa L.) with diaminobenzidine. 4 31

The mitochondrial cytochrome aa3 and b deficiencies of the [poky] cytoplasmic mutant of Neurospora crassa are partially suppressed by mutant alleles of any one of six nuclear genes, namely sup-1, sup-3, sup-4, sup-5, sup-10 and sup-14. The suppressor-induced increases in the concentration of both cytochromes are detected in the mitochondria from exponentially growing [poky] cultures, and, thus, are clearly distinguishable from the age-dependent changes in the cytochrome system that occur in cultures that approach, or have reached, the stationary phase of growth. The relative amounts of mitochondrial cytochromes aa3 and b show a direct correlation with the relative efficiency of the various sup genes as suppressors of the slow-growth phenotype of [poky]. Since [poky] is defective in mitochondrial protein synthesis due to a lack of 30 S mitochondrial ribosomal subunits, it is proposed that the six suppressors promote the assembly of functional mitochondrial ribosomes.
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PMID:Nuclear suppressors of the (poky) cytoplasmic mutant in Neurospora crassa. II. Mitochondrial cytochrome systems. 14 Jul 57

We have previously isolated six non-allelic, nuclear mutations (sui loci) that partially suppress the growth, respiratory and cytochrome abnormalities of the extranuclear [poky] mutant. A comparison of the mitochondrial ribosome profiles of suppressed and unsuppressed [poky] strains revealed that five of the six suppressors alleviate at least partially the deficiency of mitochondrial small ribosomal subunits that is associated with the [poky] genotype. Six independently isolated Group 1 extranuclear mutants, namely [exn-1], [exn-2], [exn-4-a1, [stp-b1], [SG-1] and [SG-3-A1, which have growth and cytochrome phenotypes similar to [poky] also were found to be deficient in small subunits of mitochondrial ribosomes. Using cytochrome aa3 and b production as a criterion for mitochondrial protein synthesis, it could be shown that the nuclear su I suppressors of [poky] also suppress the other six Group I extranuclear mutants. However, differences in the efficiencies of suppression by suI suppressors suggest that at least some of Group I extrachromosomal mutants are not simply re-isolates of [poky], but represent distinct extranuclear mutations.
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PMID:Nuclear suppressors of the [poky] cytoplasmic mutant in Neurospora crassa. III. Effects on other cytoplasmic mutants and on mitochondrial ribosome assembly in [poky]. 14 10

1. By the application of the principle of the sequential fragmentation of the respiratory chain, a simple-method has been developed for the isolation of phospholipid-depleted and phospholipid-rich cytochrome oxidase preparations. 2. The phospholip-rich oxidase contains about 20% lipid, including mainly phosphatidylethanolamine, phosphatidylcholine, and cardiolipin. Its enzymic activity is not stimulated by an external lipid such as asolectin. 3. The phospholipid-depleted oxidase contains less than 0.1% lipid. It is enzymically inactive in catalyzing the oxidation of reduced cytochrome c by molecular oxygen. This activity can be fully restored by asolectin; and partially restored (approximately 75%) by purified phospholipids individually or in combination. The activity can be partially restored also by phospholipid mixtures isolated from mitochondria, from the oxidase itself, and from related preparations. Among the detergents tested only Emasol-1130 and Tween 80 show some stimulatory activity. 4. The phospholipid-depleted oxidase binds with cytochrome c evidently by "protein-protein" interactions as does the phospholipid-rich or the phospholipid-replenished oxidase to form a complex with the ratio of cytochrome c to heme a of unity. The complex prepared from phospholipid-depleted cytochrome oxidase exhibits a characteristic Soret absorption maximum at 415 nm in the difference spectrum of the carbon monoxide-reacted reduced form minus the reduced form. This 415-nm maximum is abolished by the replenishment of the complex with a phospholipid or by the dissociation of the complex in cholate or in a medium of high ionic strength. When ascorbate is used as an electron donor, the complex prepared from phospholipid-depleted cytochrome oxidase does not cause the reduction of cytochrome a3 which is in dramatic contrast to the complex from the phospholipid-rich or the phospholipid-replenished oxidase. However, dithionite reduces cytochrome a3 in all of the preparations of the cytochrome c-cytochrome oxidase complex. These facts suggest that the action of phospholipid on the electron transfer in cytochrome oxidase may be at the step between cytochromes a and a3. This conclusion is substantiated by preliminary kinetic results that the electron transfer from cytochrome a to a3 is much slower in the phospholipid-depleted than in phospholipid-rich or phospholipid-replenished oxidase. On the basis of the cytochrome c content, the enzymic activity has been found to be about 10 times higher in the system with the complex (in the presence of the replenishedhe external medium unless energy is provided, and that
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PMID:Studies on cytochrome oxidase. Interactions of the cytochrome oxidase protein with phospholipids and cytochrome c. 16 52

The content of cytochromes a,b and c, the activity of marker enzymes of the matrix and inner membrane of the mitochondria: glutamate dehydrogenase and cytochrome oxidase, as well as the rate of absorption of O2 by root segments in the presence of respiratory substrates, oxygen, inhibitors of respiration, and dinitrophenol, were determined. The intensification of cell respiration in the phase of elongation is determined not so much by new formation of cytochrome components of the respiratory cycle (during this period there is an accumulation only of cytochrome c) as by reorganization of the respiratory cycle (primarily its portion NADH - cytochrome b) and synthesis of enzymes of the matrix.
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PMID:Formation of the enzymatic apparatus of respiration in growing cells. Communication II. Reorganization of the respiratory cycle of mitochondria in the corn root tip. 16 96

THE Soret spectrum of "resting" cytochrome oxidase in cytochrome-c depleted mitochondria has been determined. The spectrum obtained is dependent on the rate at which the oxidase is turning over. In the least active preparations, the spectrum is almost pure "oxidized" oxidase. With increasing activity the spectrum is converted to a mixture of "oxidized" and "oxygenated" oxidases. It is concluded that the same conformational differences between the two non-reduced forms that are found in the purified enzyme also occur in these cytochrome-c depleted mitochondria.
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PMID:The conformational states of cytochrome oxidase in the mitochondrion. 16 88

The synthesis of cytochromes aa3, b, and c has been investigated during synchronous growth in the yeast, Saccharomyces cerevisiae. These cytochromes increase in concentration continuously throughout each cell cycle, with an approximate doubling in rate during successive cycles. The rates of cytochrome formation are considerably higher in galactose-grown cultures than in cells grown in glucose. Although cytochrome aa3 increases at a continuous rate, its functional counterpart, cytochrome c oxidase, increases in stepwise fashion, with the increments occurring at the beginning of each new cell cycle. Chloramphenicol, a specific inhibitor of intramitochondrial protein synthesis, inhibits the formation of cytochrome aa3 at all stages of the cell cycle, but does not inhibit cytochrome c. Chloramphenicol exhibits a somewhat intermediate effect on cytochrome b synthesis, with transient inhibition occurring only when the drug is added prior to or during the initial part of the first cell cycle. After this time, chloramphenicol had no effect on the rate of cytochrome b synthesis. The data indicate that under our conditions of cell synchrony mitochondrial membrane formation as reflected by increments in mitochondrial cytochromes occurs by continuous accretion of new material throughout the cell cycle. Intramitochondrially synthesized polypeptide products, responsible for the formation of new cytochrome aa3, appear to be synthesized throughout the cell cycle.
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PMID:Cytochrome synthesis in synchronous cultures of the yeast, Saccharomyces cerevisiae. 16 91

Megamitochondria have been isolated from the liver of the cuprizone-fed mouse with the aid of bovine serum albumin. Phosphorylating capacities of megamitochondria, specified above, in terms of respiratory control ratios and ADP/O ratios have revealed that they are not uncoupled completely. Biochemical properties of megamitochondria which are related to the metabolism of copper have shown that copper-chelating action of cuprizone may not be directly related to the formation of megamitochondria in vivo. Namely, cytochrome contents, activities of cytochrome oxidase and monoamine oxidase and contents of copper of megamitochondria were unchanged compared with those of the control. However, contents of divalent metals such as Ca-++ and Mg-++, especially that of the former, in megamitochondria decreased significantly. It is suggested that cuprizone may alter Mg-++/Ca-++ ratios when it is administered in vivo, and that changes in the ratio might play a key role in the formation of megamitochondria.
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PMID:Mechanism of the formation of megamitochondria induced by copper-chelating agents. II. Isolation and some properties of megamitochondria from the cuprizone-treated mouse liver. 16 53


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