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)

Seven protein subunits of cytochrome c oxidase from bovine heart were isolated by gel filtration in the presence of sodium dodecyl sulphate (subunits I, II and III) and guanidine hydrochloride (subunits V, VI and VII), and ion-exchange chromatography in 6 M urea (subunit IV) after the enzyme had been dissociated in 6 M guanidine hydrochloride. When analysed by highly cross-linked sodium dodecyl sulphate/polyacrylamide gel electrophoresis in the presence of urea, the apparent molecular weights were = I, 36700; II, 24300; III, 20400; IV, 17300; V, 12300; VI, 8700: and VII, 5100. Monospecific rabbit antisera were obtained against subunits I, IV, V, VI and VII and a mixture of subunits II and III. These subunit-specific antisera with the exception of anti-I serum all cross-reacted with the detergent-solubilized native oxidase. Enzymatic studies on purified oxidase indicated that immunoglobulins against subunits II + III, IV, V, VI and VII respectively caused 25, 65, 20, 30 and 25% inhibition while anti-I immunoglobulin did not inhibit the activity. The subunit-specific antisera were used to examine the arrangements of the subunits in the membrane. Enzymatic studies using bovine heart mitochondria and rat liver mitochondrial digitonin particles showed that anti-(II + III) serum, anti-V serum and anti-VII serum all inhibited the oxidase activity while the other antisera did not. On the other hand, results of using 125I-labelled immunoglobulins showed that anti-IV, anti-V and anti-VII sera were bound to the surface of inverted vesicles (matrix side) while all other antisera were not. These results indicate that cytochrome oxidase subunits II and III are situated on the outer surface, and subunit IV is exclusively on the matrix surface while subunits V and VII are exposed on both surfaces of the mitochondrial membrane. Subunits I and VI are buried within the membrane, not exposed on either side.
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PMID:Immunological studies on cytochrome c oxidase: arrangements of protein subunits in the solubilized and membrane-bound enzyme. 21 67

The response of cytochrome oxidase to the denaturant guanidine hydrochloride (Gdn.HCl) occurs in two stages. The first stage is a sharp transition centered at 1 M Gdn.HCl, whereas the second stage occurs from 3 to 7 M Gdn.HCl. In the first phase, changes occur in several spectroscopic properties: (1) the tryptophan fluorescence increases from 37% of that of N-acetyltryptophanamide to 85%; (2) the emission maximum shifts from 328 to 333 nm; (3) the circular dichroism (CD) signal at 222 nm diminishes by 30%; and (4) the Soret CD signal at 426 nm is completely abolished. These spectroscopic changes are accompanied by complete loss of the oxidase's steady-state electron-transfer activity. Of the 13 available sulfhydryl residues, 2 are reactive in the isolated enzyme, but this number increases to almost 10 in the first stage of denaturation. Subunits III, VIb, VIc, and VII dissociate from the protein complex at 0.5 M Gdn.HCl, but only subunit VII can be recovered after gel filtration chromatography [nomenclature according to Buse et al. (1985)]. In 2.5 M Gdn.HCl, the heme groups are found with a complex consisting predominantly of subunits I, II, and IV. In the second phase of denaturation, there is further disruption in the structure of the oxidase as indicated by continued decline in the ultraviolet CD signal and shift to longer wavelength of the tryptophan emission spectrum. However, the fluorescence quantum yield and number of reactive sulfhydryl groups decrease as the denaturant level is raised. Gel filtration chromatography reveals that protein and heme form a high molecular weight aggregate at 5 M Gdn.HCl.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Subunit dissociation and protein unfolding in the bovine heart cytochrome oxidase complex induced by guanidine hydrochloride. 284 38

The optical properties of Pseudomonas cytochrome oxidase (ferrocytochrome-c:oxygen oxidoreductase, EC 1.9.3.2) were monitored as a function of guanidine hydrochloride (Gdn X HCl) concentration to probe for differential stabilization of its prosthetic groups, heme d1 and heme c. The protein fluorescence intensity increased with the Gdn X HCl concentration, revealing two transitions, a sharp one between 1.3 and 1.5 M Gdn X HCl, and a second less well defined extending from 2.5 to 4.5 M. Only the transition at the lower Gdn X HCl concentrations was present in titrations followed using the emission maxima. The spectral maximum for native Pseudomonas cytochrome oxidase was at approx. 335 nm and shifted to approx. 350 nm above 2 M Gdn X HCl. The heme d1 absorbance at 638 nm decreased with increasing [Gdn X HCl], giving a transition at 1.3-1.5 M, and no transition up to 4 M Gdn X HCl when the heme c was monitored at 525 nm. Along with the decrease at 638 nm, an absorption band appeared at 681 nm, suggesting heme d1 release into solution. Fluorescence titration of heme d1-depleted enzyme, prepared by gel filtration, showed a single transition similar to the transition occurring in the intact enzyme at high Gdn X HCl concentrations. Circular dichroism spectra revealed clearly distinguishable transitions for the heme d1 and heme c near 1.5 and 3.0 M Gdn X HCl, respectively. These results suggest that the two hemes are in regions of the protein with different stabilities which may represent distinct structural domains.
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PMID:Perturbation of Pseudomonas cytochrome oxidase by guanidine hydrochloride to detect differential stabilization of the heme d1 and heme c moieties. 301 Oct 97

Treatment of both Candida apicola IMET 43747 and Candida bombicola ATCC 22214 with N-methyl-N'-nitro-N-nitroso guanidine resulted in formation of auxotrophic mutants and cytochrome oxidase negative mutants. The deficiency of intact cytochrome oxidase did not affect the ability to produce sophorose lipid. This indicates that intact mitochondrial energy supplying system is not necessary for the production of the extracellular sophorose lipids by both Candida yeasts.
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PMID:Petite mutants of sophorolipid-producing Candida yeasts. 820 65

The unfolding of the CuA domain of cytochrome oxidase from the thermophilic bacterium Thermus thermophilus, induced by guanidine hydrochloride (GuHCl)1 at different temperatures, has been monitored by CD as well by electronic absorption (with the oxidized protein) and by fluorescence (with the reduced protein). The same unfolding curves were obtained with the different methods, providing evidence for a two-state model for the unfolding equilibrium. This was also supported by the shape of the unfolding equilibrium curves and by the observed refolding of the unfolded, oxidized protein on dilution of the denaturant. The oxidized protein cannot be unfolded by GuHCl at room temperature, and it was found to be thermally very stable as well, since, even in the presence of 7 M GuHCl, it is not fully unfolded until above 80 degrees C. For the reduced protein at room temperature, the unfolding equilibrium curve yielded a folding free energy of -65 kJ/mol. The corresponding value for the oxidized protein (-85 kJ/mol) could be estimated indirectly from a thermodynamic cycle connecting the folded and unfolded forms in both oxidation states and the known reduction potentials of the metal site in the folded and unfolded states; the potential is increased on unfolding, consistent with the higher folding stability of the oxidized form. The difference in folding stability between the oxidized and reduced proteins (20 kJ/mol) is exceptionally high, and this is ascribed to the unique structure of the dinuclear CuA site. The unfolded, reduced protein was found to refold partially on oxidation with ferricyanide.
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PMID:Effect of redox state on the folding free energy of a thermostable electron-transfer metalloprotein: the CuA domain of cytochrome oxidase from Thermus thermophilus. 948 71

On the basis of our own experimental data and analysis of data from the literature the existence of nitric oxide cycle in mammals is substantiated. Two components underlie the nitric oxide cycle: 1) the reaction catalyzed by NO-synthases (constitutive, inducible, and endothelial--NOS-I, -II, and -III); and 2) the nitrite-reductase reactions catalyzed by electron-donor systems with the participation of NADH, NADPH, flavoproteins, and heme-containing proteins. In mammalian cells NO is enzymatically formed from terminal guanidine nitrogen of L-arginine by a family of at least three distinct NOS isoenzymes. As a result of nonenzymatic/enzymatic NO oxidation, NO2- and NO3- ions are formed: L-Arg --> NO --> NO2-/NO3-. The reduction of NO2- ions to NO occurs via the nitrite-reductasereaction: NO2- + e- --> NO. The reduction of NO2- ions to NO is realized by electron-donor systems with the participation of NADH, NADPH, flavoproteins, and cytochrome oxidase in mitochondria and by NADH, NADPH, flavoproteins, and cytochrome P-450 in endoplasmic reticulum. In erythrocytes the reduction of NO2- ions to NO is catalyzed by electron-donor systems with participation of NADH, NADPH, flavoproteins, and deoxy-hemoglobin. The role of ascorbic acid and reduced glutathione should be noted among low-molecular-weight compounds. Thus, the presence of the nitric oxide cycle provides the cyclic transformation as follows: L-arginine --> NO --> NO2-/NO3- --> NO.
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PMID:NO-synthase and nitrite-reductase components of nitric oxide cycle. 972 40