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

Lipid-depleted cytochrome c oxidase (EC 1.9.3.1) containing less than 20 microgram lipids per milligram protein was reconstituted with pure phospholipids of well-defined chemical structure and fatty acid composition without using detergents and (or) sonication. For the maximal restoration of electron transport activity, lipid-depleted cytochrome c oxidase required acidic phospholipds such as phosphatidylglycerol or phosphatidylserine or lysophospholipids such as lysophosphatidylcholine or lysophosphatidic acid, but no specific phospholipid fatty acid composition was necessary. The organization of the lipid environment of the reconstituted cytochrome c oxidase, having a well-defined lipid composition, morphology, and a high specific activity, was examined by electron spin resonance spectroscopy using 2-(14-carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxyl (16-doxyl stearic acid) and 16-doxyl stearic acid - containing phosphatidylglycerol. The presence of boundary lipid was established in both lamellar and micellar organizations of reconstituted cytochrome c oxidase and was not necessarily related to the enzymatic activity of the complex. Our results have established that aside from structural considerations, the boundary lipid, at least in the reconstituted cytochrome c oxidase, is a necessary but not sufficient condition for the enzymatic expression of cytochrome c oxidase.
 ...
PMID:Spin-label study of the relation between enzymatic activity and lipid-protein organization in reconstituted cytochrome c oxidase. 21 92

Deuterium and 31P nuclear magnetic resonance have been employed in an investigation of the effect of cytochrome c oxidase (EC 1.9.3.1) on the structure of lecithin bilayers. Cytochrome c oxidase was isolated from beef heart mitochondria in lipid-free form and reconstituted as a functional enzyme in bilayers composed of synthetic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine. Two separate reconstitution experiments were performed in which the lipid was selectively deuterated either at the C-5' or at the C-14' segment of the palmitic acyl chain. The phospholipid-to-protein ratio of both reconstituted complexes was 0.74 (mg/mg), corresponding to about 200 molecules lipid per molecule cytochrome c oxidase. The deuterium quadrupole splitting deltanuQ, and the phosphorus chemical shielding anisotropy, deltasigma, of the cytochrome c oxidase-phospholipid recombinants were measured as a function of temperature and compared to the results obtained for the pure lipid membrane without protein for the pure lipid membrane without protein. deltanuQ and deltasigma are highly sensitive to the structural organization of the lipid membrane and these measurements demonstrate that the incorporation of cytochrome c oxidase into phosphatidylcholine bilayers leads to a more disordered conformational state of the lipids. This result can be explained by a rapid exchange between lipids in direct contact with hydrophobic protein and those further away from it (exchange rate greater than 10(4) Hz). The irregular protein surface is sensed by all lipid molecules and induces a more disordered bilayer structure. In contrast to previous interpretations, our measurements do not suggest a special type of boundary lipid.
 ...
PMID:Lipid-protein interaction in reconstituted cytochrome c oxidase/phospholipid membranes. 21 16

Three nuclear mutants of Neurospora crassa, temperature-sensitive for the synthesis of cytochrome aa3 have been isolated. When grown at 41 degrees C the mutants have large amounts of KCN-insensitive respiration, reduced amounts of cytochrome aa3 and cytochrome c oxidase activity, and grow more slowly than wild-type cultures grown at the same temperature. When the mutants are grown at 23 degrees C, they are virtually indistinguishable from wild-type strains. The mutants were selected on the basis of their slow growth at 41 degrees C in medium containing salicylhydroxamic acid, and by their inability to reduce 2,3,5-triphenyltetrazolium chloride at 41 degrees c. The selecttion technique was designed to eliminate mutants that did not carry thermolabile electron transport chain components. However, studies on the thermolability of the cytochrome oxidase activity in isolated mitochondria indicate that the enzyme of the mutants is no more susceptible to heat denaturation than is the enzyme in wild-type mitochondria. This suggests that the synthesis or assembly of cytochrome aa3 may be altered in the mutants at the restrictive temperature.
 ...
PMID:Nuclear mutants of Neurospora crassa temperature-sensitive for the synthesis of cytochrome aa3. I. Isolation and preliminary characterization. 21

Horse heart cytochrome c was treated with methylsulfonylethyloxycarbonyl succinimide (Msc-ONSu) to give fully N(epsilon)-protected cytochrome c. Treatment of this derivative with a hard base for 15 sec regenerated the native tetrahectapeptide chain. CNBr degradation of the protected compound produced three fragments bearing only protective Msc functions on epsilon-amino groups. The fragment comprising the sequence 81-104 was isolated from the mixture and acylated with N-hydroxysuccinimidyl-t-butyloxycarbonyl-L-methioninate. The resulting pentacosapeptide derivative was partially deprotected by treatment with acid and condensed in good yield (65%) with fully synthetic N(alpha66), N(epsilon72,73,79)- tetra-Msc-cytochrome-c-(66-79)-tetradecapeptide azide. This pathway is preferred because the pentadecapeptide azide derivative 66-80 acylated the N(epsilon)-protected tetracosapeptide sequence 81-104 in an unpredictable manner. Subsequent treatment of the product with a base produced unprotected semisynthetic cytochrome-c-(66-104)-nonatriacontapeptide, which is known to undergo acylation by unprotected [Hse(65)]cytochrome-c-(1-65)-pentahexacontapeptide lactone. The high specificity of this condensation is ascribed to "conformation direction." Semisynthetic [Hse(65)]cytochrome c thus prepared reacts like native cytochrome c with a succinate cytochrome c reductase preparation and with cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1). This semisynthetic strategy may provide a rapid route for the production of cytochrome c analogs modified in the highly conservative sequence 66-80.
 ...
PMID:Semisynthetic horse heart [65-homoserine]cytochrome c from three fragments. 21 5

A photoreductive titration of the resonance Raman (RR) spectra of cytochrome c oxidase in whole mitochondria was recorded by exploiting the preferential enhancement of the Raman signals of reduced cytochrome oxidase excited at 441.6 nm. When the sample was cooled to about--10 degrees C, it was possible to slow down the photoreductive effect of the laser and to record RR spectra at various states of reduction. Compared to the earliest recorded scan (most oxidized), the dithionite-reduced sample shows the appearance of new bands at 216, 363, 560, and 1665 cm-1. At intermediate stages of photoreduction, the 216- and 560-cm-1 bands appear before the 363- and 1665-cm-1 bands; photoreduction induces full intensity in the former bands, whereas the latter bands are photoreduced to 50% of the dithionite-reduced intensity. The relative intensities of a doublet at 1609--1623 cm-1 are affected by reduction: the band at 1609 cm-1 is weaker in the earlier scans; in later scans this band has grown to equal intensity with the 1623-cm-1 band. We conclude that this reductive titration of the RR spectrum of cytochrome c oxidase reflects three states in its reduction. The behavior of the doublet at 1609--1623 cm-1 suggests that the two hemes are nonequivalent but interacting. The band at 216 cm-1 may be indicative of an iron-copper interaction that is affected by the presence of external ligands.
 ...
PMID:Photoreductive titration of the resonance Raman spectra of cytochrome oxidase in whole mitochondria. 21 87

X-ray absorption edge spectroscopy has been used to study the copper of 1--2 mM cytochrome c oxidase in the resting oxidized, mixed-valence, and fully reduced states. A comparison was made of this protein with copper complexes and with natural and artificial copper proteins. Spectra were obtained with synchrotron radiation from the SPEAR storage ring using highly sensitive fluorescence detectors. Temperatures of -80 to -120 degrees C were employed further to improve the stability of the samples and to avoid the possibility of either auto- or photon-induced reduction of the materials, which might have occurred in previous studies. In order to characterize the valence states of the Cu and Fe components, the samples were monitored by infrared and visible spectroscopy before and after irradiation by the X-ray beam. The combination of the optical and X-ray absorption techniques has afforded a deconvolution of the four species of copper in the various states of cytochrome c oxidase and the tentative assignment of Cu alpha, the copper redox coupled to the heme alpha of cytochrome alpha, as a highly covalent type of copper and Cu alpha 3, the copper of cytochrome alpha 3, as a more ionic 'blue' type I copper. The implications of these findings upon the mechanism of action of cytochrome oxidase are briefly outlined.
 ...
PMID:The nature of the copper atoms of cytochrome c oxidase as studied by optical and x-ray absorption edge spectroscopy. 22 13

1. In the absence of cytochrome c, ferrocyanide or ferrous sulphate reduces cytochrome c oxidase (EC 1.9.3.1), but no continuous oxygen uptake ensues, as it does with N,N,N',N'-tetramethyl-p-phenylenediamine or reduced phenazine methosulphate as reductants, unless a substoichiometric amount of cytochrome c or an excess of clupein is present. Cytochrome c cannot be replaced by porphyrin cytochrome c. 2. Cytochrome c, porphyrin cytochrome c and clupein all stimulate the reduction of cytochrome aa3 by ferrocyanide. 3. A model is proposed to explain these findings in which a high-affinity site for cytochrome c on the oxidase regulates the access of hydrophilic electron donors to a low-affinity site, and reduction via the high-affinity site is required for continuous oxygen uptake. 4. Furthermore, it is shown that upon reaction of oxidase with ferrocyanide, cyano-oxidase is formed.
 ...
PMID:Ferrocyanide as electron donor to cytochrome aa3. Cytochrome c requirement for oxygen uptake. 22 35

Under continuous illumination the CO binding curve of reduced carboxy-cytochrome c oxidase maintains the shape of the binding curve in the dark. The apparent dissociation constant calculated from the binding curves at various light intensities is a linear function of the light intensity. Marked differences are observed between the light-induced difference spectra of the fully reduced carboxy-cytochrome c oxidase and the mixed-valence carboxy-cytochrome c oxidase. These differences are enhanced in the presence of ferricyanide as an electron acceptor and are explained by partial oxidation of cytochrome a3 in the mixed-valence enzyme after photodissociation. Upon addition of CO to partially reduced formate cytochrome c oxidase (a2+a3 3+ . HCOOH) the cytochrome a3 2+. CO compound is formed completely with a concomitant oxidation of cytochrome a and the Cu associated with cytochrome a. During photodissociation of the CO compound the formate rebinds to cytochrome a3 and cytochrome a and its associated Cu are simultaneously reduced. These electron transfer processes are fully reversible since in the dark the a3 3+ . HCOOH compound is dissociated slowly with a concomitant formation of the a3 2+ . CO compound and oxidation of cytochrome a. When these experiments are carried out in the presence of cytochrome c, both cytochrome c and cytochrome a are reduced upon illumination of the mixed-valence carboxy-cytochrome c oxidase. In the dark both cytochrome c and cytochrome a are reoxidized when formate dissociates from cytochrome a3 and the a2+ 3 . CO compound is formed back. Thus, in this system we are able to reverse and to modulate the redox state of the different components of the final part of the respiratory chain by light.
 ...
PMID:Electron-transfer processes in carboxy-cytochrome c oxidase after photodissociation of cytochrome a3 2+ . CO. 22 38

The mitochondria of cytochrome-aa3-deficient Neurospora crassa mutants were screened for the seven polypeptide constiuents of cytochrome c oxidase. The polypeptides of the holoenzyme and the unassembled or partially assembled subunits were detected by sodium dodecyl sulfate/acrylamide gel electrophoresis of immunoprecipitates obtained with antiserum to the holoenzyme as well as to several individual subunits. With respect to the mitochondrially synthesized polypeptides of the oxidase, subunits 1 to 3, the results obtained from the analysis of immunoprecipitates were confirmed through the direct electrophoretic analysis of mitochondrial translation products. The results were as follows. 1. The mitochondria of the cya-2-8 and cya-3-16 nuclear mutants and the [exn-5] cytoplasmic mutant contained a protein complex immunoprecipitated by anti-holoenzyme antibody and composed of the complete set of the seven cytochrome oxidase polypeptides. Only the oxidase subunits 5 and 6 were immunoprecipitated by anti-holoenzyme antibody from the mitochondria of the cyt-2-1 and 299-1 nuclear mutants, even though at least some of the mitochondrially synthesized polypeptides were detected in both mutants by subunit specific immunoprecipitation. 2. A 'subunit 1' polypeptide larger than the authentic subunit-1 polypeptide of wild-type cytochrome oxidase was found in the mitochondria from two nuclear mutants, cyt-2-1, and 299-1 and the [mi-3] cytoplasmic mutant. This larger polypeptide may be an unprocessed precursor of the 'mature' subunit 1 protein of the holoenzyme. No changes in the apparent molecular weights were found for the polypeptide subunits of cytochrome oxidase in mitochondria of the [exn-5] cytoplasmic mutant and the cya-2-8 and cya-4-23 nuclear mutants. 3. A nuclear mutant, 299-1, lacks the mitochondrially synthesized subunit-2 polypeptide of cytochrome oxidase. When cells were labelled in the presence of cycloheximide, the subunit 2 content of mitochondria from mutants [exn-5], cya-2-8, cya-3-16 and cya-4-23 was lower than in mitochondria from wild-type. This deficiency, however, does not appear to be sufficiently severe to fully account for the lack of cytochrome aa3 in these mutants. The cya-4-23 nuclear mutant either is severely deficient in or lacks cytochrome oxidase subunits 5 and 6. On the basis of these and previously reported observations, it is proposed that the cytochrome oxidase deficiencies of as many as seven of the eight N. crassa cytochrome-aa3-deficient mutants could be caused by genetically imposed alterations in regulatory systems controlling the production of different components of the enzyme.
 ...
PMID:Cytochrome c oxidase subunits in nuclear and extranuclear cytochrome-aa3-deficient mutants of Neurospora crassa. 22 48

The resonance Raman (RR) spectra of oxidized, reduced, and oxidized cyanide-bound cytochrome c oxidase with excitation at several wavelengths in the 600-nm region are presented. No evidence is found for laser-induced photoreduction of the oxidized protein with irradiation at lambda approximately 600 nm at 195 K, in contrast to the predominance of this process upon irradiation in the Soret region at this temperature. The Raman spectra of all three protein species are very similar, and there are no Raman bands which are readily assignable to either cytochrome a or cytochrome a3 exclusively. The Raman spectra of the three protein species do, however, exhibit a number of bands not observed in the RR spectra of other hemoproteins upon exicitation in their visible absorption bands. In particular, strong Raman bands are observed in the low-frequency region of the RR spectra (less than 500 cm-1). The frequencies of these bands are similar to those of the copper-ligand vibrations observed in the RR spectra of type 1 copper proteins upon excitation in the 600-nm absorption band characteristic of these proteins. In cytochrome c oxidase, these bands do not disappear upon reduction of the protein and, therefore, cannot be attributed to copper-ligand vibrations. Thus, all the observed RR bands are associated with the two heme A moieties in the enzyme.
 ...
PMID:Resonance Raman spectra of cytochrome c oxidase. Excitation in the 600-nm region. 22 25


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>