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)

The CO-binding kinetics of cytochrome a3, in isolated, detergent-solubilized cytochrome oxidase have been studied by flash photolysis over wide ranges of CO concentration and temperature. The results strongly suggest that CO has an intermediate bound state in its path to the final bound state at the heme iron. In the temperture range 230-273 K in frozen aqueous solutions, the recombination rates depend upon CO concentration; at low CO concentrations the kinetics are biphasic. The rate of the faster process depends upon the detergent concentration, that of the slower process upon the salt concentration. In addition, the faster process depends upon the amount of CO photodissociated. It is concluded that the cytochrome oxidase molecules are aggregated in regions that contain detergent and possibly some lipids. The regions retain considerable fluid character well below the macroscopic freezing point of the solution. The faster phase of the recombination is interpreted as the rebinding of CO molecules that remain in the fluid region after photodissociation. The slower phase would then be due to the migration of some dissociated CO out into surrounding frozen solvent. The non-Arrhenius behavior of both phase probably represents partial melting of the medium; preliminary NMR measurements of mobile protons support this hypothesis. Many of the kinetic features described here are also seen in mitochondria; thus the detergent-solubilized cytochrome oxidase may be a useful model system for the ligand-binding behavior of the enzyme in the mitochondrial membrane.
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PMID:Low-temperature flash photolysis studies of cytochrome oxidase and its environment. 20 10

We have recorded 100.6-MHz high-resolution solid-state 13C-NMR spectra of crystalline cytochrome-c oxidase from bovine heart muscle and hen egg-white lysozyme, to compare conformation and dynamics of a typical membrane-protein complex with those of lysozyme. The absence of severe interference with the solid-state 13C-NMR spectra, from both the line broadenings from paramagnetic centers and overlapping of intense detergent signals, provided spectral resolution of 13C-NMR feature of cytochrome-c oxidase crystals comparable to that of lysozyme crystal and better than that of dissolved or lyophilized samples. In fact, the observed peak intensities of the polar heads of the detergents BL8SY and Brij 35 were only about 10% and 3% of the anticipated values, respectively. The dynamic behavior of the backbone and side chains of cytochrome-c oxidase was compared with that of lysozyme on the basis of the 13C spin-lattice relaxation times (T1): the backbone of the cytochrome-c oxidase turned out to be more flexible than that of lysozyme. Molecular motions of the detergent molecules attached to the proteins are found to be highly heterogeneous. Detergent molecules undergo rapid tumbling motions in the crystals in about 10 ns as detected by T1. In addition to rapid motions, slow motions were detected by 1H spin-lattice relaxation time in the rotating frame (TH1 rho) and cross-polarization time (TCH), together with data from static spectra, indicating that the aliphatic portion of the detergent interacts more strongly with hydrophobic protein surfaces than do the polar heads.
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PMID:A high-resolution solid-state 13C-NMR study on crystalline bovine heart cytochrome-c oxidase and lysozyme. Dynamic behavior of protein and detergent in the complex. 132 66

Previous studies on mitochondrial targeting presequences have indicated that formation of an amphiphillic helix may be required for efficient targeting of the precursor protein into mitochondria, but the structural details are not well understood. We have used CD and NMR spectroscopy to characterize in detail the structure of a synthetic peptide corresponding to the presequence for the beta-subunit of F1-ATPase, a mitochondrial matrix protein. Although this peptide is essentially unstructured in water, alpha-helix formation is induced when the peptide is placed in structure-promoting environments, such as SDS micelles or aqueous trifluoroethanol (TFE). In 50% TFE (by volume), the peptide is in dynamic equilibrium between random coil and alpha-helical conformations, with a significant population of alpha-helix throughout the entire peptide. The helix is somewhat more stable in the N-terminal part of the presequence (residues 4-10), and this result is consistent with the structure proposed previously for the presequence of another mitochondrial matrix protein, yeast cytochrome oxidase subunit IV. Addition of increasing amounts of TFE causes the alpha-helical content to increase even further, and the TFE titration data for the presequence peptide of the F1-ATPase beta-subunit are not consistent with a single, cooperative transition from random coil to alpha-helix. There is evidence that helix formation is initiated in two different regions of the peptide. This result helps to explain the redundancy of the targeting information contained in the presequence for the F1-ATPase beta-subunit.
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PMID:Conformational analysis of a mitochondrial presequence derived from the F1-ATPase beta-subunit by CD and NMR spectroscopy. 139 Sep 13

This paper concerns an NMR study of cytochromes c in an effort to understand the coupling of redox state changes with protein conformation and proton movement. The objective is to find a model which will allow us to understand electron/proton diffusion coupling as seen in cytochrome oxidase and envisaged in one description of energy transduction.
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PMID:Uncoupled and coupled electron transfer reactions. 164 24

The structural comparison of copper-containing proteins has provided a new dimension to the relationships suggested by sequence similarities. Ryden (1988) summarized the putative relationships, suggesting that a primordial single-domain cupredoxin evolved into the multidomain copper oxidases. The structures have revealed the fact that the differences reside primarily in insertions and deletions at junctions between secondary-structure elements. The mechanism of evolution (e.g., integration of new sequences into regions not essential to the Greek key fold) remains unknown. Which of the properties of a cupredoxin fold are necessary for function is the subject of site-directed mutagenesis studies. Can two of the ligands be interchanged (e.g., the upstream histidine and partially answered by the multidomain copper oxidase structure. The Tyr-Cys-Thr sequence in plastocyanin (in which threonine is a member of the hydrogen-bonding pair) is homologous with the His-Cys-His sequence in ascorbate oxidase. In the latter electron transfer is believed to flow from the type I copper (bound by the cysteine) to the trinuclear cluster, probably via these histidine residues. Hence, one might infer that the tyrosine and threonine have some role in electron transfer. Tyr-83 has been previously implicated in NMR studies as a primary site of electron transfer. The multi-copper protein structures have revealed interesting new features. The extra coppers are bound at domain interfaces, and can be single metals or the novel trinuclear cluster, depending on the availability of liganding histidines. A structural model of ceruloplasmin suggests that it will have at least two type I sites and, possibly, a third type I site such as stellacyanin (no methionine ligand), as well as a binding site for a trinuclear cluster. The similarity of the sequences of N2O reductases and a domain of cytochrome oxidase to the sequences of proteins with known structures suggests that these, too, will have Greek key domains. Galactose oxidase and hemocyanin do not have Greek key folds in their functional domains, although each does have a Greek key domain. The need for a Greek key fold remains obscure. The apoproteins are clearly stable without metals; there are examples other than immunoglobulins of Greek key folds. So far copper seems to be found in a very limited subset of structures; other chapters in this volume show that zinc, for example, has a much wider variety of environments in proteins, as does iron. It may be that the copper-containing Greek key proteins represent a very small evolutionary niche.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Copper protein structures. 179 5

The relationship between oxygen concentrations in arteries, cytosol, and mitochondria and high energy phosphate metabolism was studied in perfused rat hearts subjected to low and high workloads during gradual hypoxia. PCr, ATP, and Pi were measured by 31P-NMR. Myoglobin oxygenation and cytochrome aa3 oxidation were measured by the optical method. When influent oxygen tension was decreased gradually, PCr, ATP, %MbO2, %Cytaa3, cardiac work and MvO2 decreased while Pi and Pi/PCr increased in Langendorff and working hearts. These changes occurred, however, at higher PaO2 values in working hearts. The decrease of %MbO2 and %Cytaa3 in Langendorff hearts was parallel where the ratio of %MbO2 / %Cytaa3 was 1:1. However, this ratio was more than 1:1 in working hearts. It had been demonstrated that oxygen gradients change with changing oxygen consumption. Metabolic and heart work changes occurred simultaneously and significant changes occurred at low levels of %MbO2 and %Cytaa3. Some differences were observed between Langendorff and working hearts. Oxidative phosphorylation is a good indicator of ATP synthesis during hypoxia and is regulated by the intracellular oxygen concentration as well as oxygen gradients.
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PMID:Oxygen dependence of energy state and cardiac work in the perfused rat heart. 196 60

Validation of a toxicity testing model concerning energy metabolism was attempted by evaluating the oxygen supply and energy state in an isolated perfused rat kidney of single-pass preparation without albumin. Perfusion was performed at a temperature of 31 degrees C, flow rate of 11.0 mL/g/min, and pressure of 81-104 mmHg. The perfusate was saturated with 95% O2/5% CO2. After preperfusion for 30 min, the redox states of cytochrome aa3 and c and pyridine nucleotides (PN) in the perfused kidney were measured to be stable for 90 min by a scanning reflectance spectrophotometry and surface fluorometry, respectively. During the same period, the contents of ATP and inorganic phosphate (Pi) in the perfused kidney were also measured to be stable by 31P-NMR spectroscopy. The oxygen supply to the cell was more than the amount required for the basal metabolism of the cell. For assessment of the effects of chemical agents on the renal cell metabolism, this preparation of the perfused rat kidney was considered to have several advantages, despite some of its inherent limitations in the function of the kidney.
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PMID:Validation of a toxicity testing model by evaluating oxygen supply and energy state in the isolated perfused rat kidney. Single-pass preparation without albumin. 205 52

Deuterium and phosphorus nuclear magnetic resonance techniques were used to study the interaction of the mitochondrial precursor protein apocytochrome c with headgroup-deuterated (dioleoylphosphatidyl-L-[2-2H1]serine) and acyl chain deuterated (1,2-[11,11-2H2]dioleoylphosphatidylserine) dispersions. Binding of the protein to dioleoylphosphatidylserine liposomes results in phosphorus nuclear magnetic resonance spectra typical of phospholipids undergoing fast axial rotation in extended liquid-crystalline bilayers with a reduced residual chemical shift anisotropy and an increased line width. 2H NMR spectra on headgroup-deuterated dioleoylphosphatidylserine dispersions showed a decrease in quadrupolar splitting and a broadening of the signal on interaction with apocytochrome c. Addition of increasing amounts of apocytochrome c to the acyl chain deuterated dioleoylphosphatidylserine dispersions results in the gradual appearance of a second component in the spectra with a 44% reduced quadrupolar splitting. Such large reduction of the quadrupolar splitting has never been observed for any protein studied yet. The lipid structures corresponding to these two components could be separated by sucrose gradient centrifugation, demonstrating the existence of two macroscopic phases. In mixtures of phosphatidylserine and phosphatidylcholine similar effects are observed. The induction of a new spectral component with a well-defined reduced quadrupolar splitting seems to be confined to the N-terminus since addition of a small hydrophilic amino-terminal peptide (residues 1-38) also induces a second component with a strongly reduced quadrupolar splitting. A chemically synthesized peptide corresponding to amino acid residues 2-17 of the presequence of the mitochondrial protein cytochrome oxidase subunit IV also has a large perturbing effect on the order of the acyl chains, indicating that the observed effects may be a property shared by many mitochondrial precursor proteins. In contrast, binding of the mature protein, cytochrome c, to acyl chain deuterated phosphatidylserine dispersions has no effect on the deuterium and phosphorus nuclear magnetic resonance spectra, thereby demonstrating precursor-specific perturbation of the phospholipid order. The inability of holocytochrome c to perturb the phospholipid order is due to folding of this protein, since unfolding of cytochrome c by heat or urea treatment results in similar effects on dioleoylphosphatidylserine bilayers, as observed for the unfolded precursor. Implications of these data for the import of apocytochrome c into mitochondria will be discussed.
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PMID:The mitochondrial precursor protein apocytochrome c strongly influences the order of the headgroup and acyl chains of phosphatidylserine dispersions. A 2H and 31P NMR study. 215 98

Dimeric and monomeric forms of mitochondrial cytochrome oxidase (EC 1.9.3.1) have been examined using 1H NMR spectroscopy. Paramagnetically shifted resonances were detected in spectra of the monomeric protein. Studies of this protein in a number of oxidation and ligation states have assigned these resonances to ferrihaem a. The temperature and pH dependence of this new probe of haem a environment is reported.
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PMID:A 1H NMR study of bovine cytochrome oxidase. Paramagnetically shifted resonances of haem a. 255 87

The clinical and biochemical findings of 14 patients with an isolated defect of the bc1 complex have been summarized. The heterogeneity of this group of disorders reflects the severity and tissue specific expression of the defect and the complexity of this multisubunit protein with components that are coded on both nuclear and mitochondrial DNA. The data on several patients with a combined defect of cytochrome oxidase and the bc1 complex or with multiple respiratory chain defects have also been presented and discussed in relation to our knowledge of the biosynthesis and assembly of the respiratory chain complexes. The severity of the defect in vivo is illustrated in one patient with isolated complex III deficiency by measurement of O2 consumption and CO2 production following exercise, or by 31P-NMR. The latter also provides a means by which response to therapy can be followed.
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PMID:Defects in the cytochrome bc1 complex in mitochondrial diseases. 284 8


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