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1.
Y Orii H Shimada T Nozawa M Hatano 《Biochemical and biophysical research communications》1977,76(4):983-988
A possibility of a heme-heme interaction between the heme and heme moieties in nitrite reductase was examined by using magnetic and natural circular dichroism. The MCD of the heme moiety in the ferric enzyme was similar to that of mammalian ferricytochrome in shape and intensity, whereas in the reduced state the MCD intensity was considerably smaller than that of ferrocytochrome . When the heme moiety was perturbed by the complex formation with CO, imidazole or cyanide as well as by pH changes, the depressed MCD was restored to the MCD level of mammalian ferrocytochrome , accompanying conformational changes around the prosthetic groups. Thus, it was concluded that the heme-heme interaction exists only in the reduced enzyme and that this interaction is released under appropriate conditions. 相似文献
2.
The low temperature optical spectra in the region of the Q00 (α-band) and Q01 (β-band) transitions of model heme complexes for - and c-type cytochromes were measured and the results discussed in terms of the similarities and differences to the spectra of horse heart cytochrome and other hemeproteins. Comparisons of the resolved vibronic components of the Q01 and β′ bands were made to the recent resonance Raman spectra of hemeproteins. Tentative assignment of the β′ band to Q02 type transitions has been proposed. 相似文献
3.
Charge distribution in electron transport components: cytochrome c and cytochrome c oxidase mixtures
Mixtures of cytochrome oxidase and cytochrome have been titrated by coulometrically generated reductant, methyl viologen radical cation, and physiological oxidant, O2. Charge distribution among the heme components in mixtures of these two redox enzymes has been evaluated by monitoring the absorbance changes at 605 and 550 nm. Differences in the pathway of the electron transfer process during a reduction cycle as compared to an oxidation cycle are indicated by variations found in the absorbance behavior of the heme components during successive reductive and oxidative titrations. It is apparent that the potential of the cytochrome heme is dependent upon whether oxidation or reduction is occurring. 相似文献
4.
The addition of formate to oxidized cytochrome oxidase (ferrocytochrome : oxygen oxidoreductase, EC 1.9.3.1) causes the appearance of a high spin heme signal at g = 6 and a splitting of g = 3 signal to g = 2.98 and 3.07. When formate-cytochrome oxidase is reduced, the g = 2.98 signal decreases significantly. The spectrophotometric studies showed that formate is a specific ligand to cytochrome 3. Data suggest that binding of formate to oxidized cytochrome oxidase produces a ligand-3 interaction leading to the splitting of g = 3 signal hitherto considered as due to cytochrome . Thus both cytochrome and 3 contribute to the resonance of g = 3 signal of cytochrome oxidase. 相似文献
5.
J.K. Blasie J.M. Pachence A. Tavormina P.L. Dutton J. Stamatoff P. Eisenberger G. Brown 《BBA》1983,723(3):350-357
The technique of resonance X-ray diffraction (Blasie, J.K. and Stamatoff, J. (1981) Annu. Rev. Biophys. Bioeng. 10, 451–452) utilizing synchrotron radiation was used to determine the locations of the cytochrome c heme iron atom and the photosynthetic reaction center iron atom within the profile of a reconstituted membrane. The accuracy of these determinations was better than ±2 ?. The cytochrome c heme iron atom → reaction center iron atom vector was determined to have a magnitude of approx. 44 ? projected onto the membrane profile and to span most of the lipid hydrocarbon core of the membrane profile. Since the reaction center iron atom interacts magnetically with the primary quinone electron acceptor QI over a distance of less than 10 ?, the primary light-induced electron-transfer reactions for this system generate the electric charge separation between oxidized cytochrome c+ and Fe-Q?I across most (approx. ) of the membrane profile including most or all of the lipid hydrocarbon core of the membrane. 相似文献
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7.
The flow measurement of each component in each compartment is important in works on transport phenomena in a biological system. The method of flow measurement was studied adopting the capacitor concept derived from network thermodynamics.A biologically active component i in a compartment is defined as follows, where the total quantity ni consists of a measurable form ni (free form, conc. c1) and concealed form n2 (conc, c2). Capacitor for the species i of a compartment is defined as follows, , Thus flow of each component is expressed as, , Method of determination of capacitor coefficients A and B by titration experiment was also considered. For an experimental case, the capacitance for H+ of blood compartment was determined. The relationship between the capacitor concept and the buffer value of Van Slyke was discussed. 相似文献
8.
hemeproteins P-450, and cross react with antibodies to P-450CAM and P-450LM-2. Anti P-450CAM IgG and phenobarbital, each bound to Sepharose 4B, were effective in purification of P-450; the latter was more convenient. The amino acid composition of highly purified P-450 resembles the compositions of P-450CAM and P-450LM-2. These results suggest that P-450 heme proteins of unrelated substrate specificities may nevertheless contain similar structural features. 相似文献
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10.
(1) Alkyl sugar inhibition of d-allose uptake into adipocytes has been used to explore the spatial requirements of the external sugar transport site in insulin-treated cells. α-methyl and β-methyl glucosides show low affinity indicating very little space around C-1. The high affinity of d-glucosamine (Ki = 9.05 ± 0.66 mM) is lost by N-acetylation. shows no detectable affinity, indicating that a bulky group at C-2 is not accepted. Similarly (Ki = 42.1 ± 7.5 mM) has lower affinity than (Ki = 5.14 ± 0.32 mM) indicating very little space around C-2 but much more around C-3. A reduction in affinity does occur if a propyl group is introduced into the C-3 position. The Ki for is 11.26 ± 2.12 mM. (Ki = 87.2 ± 17.9 mM) and (Ki = 78.07 ± 12.6 mM) show low affinity compared with d-galactose and d-glucose, indicating steric constraints around C-6. High affinity is restored in (Ki = 4.66 ± 0.23 mM) possibly indicating a hydrophobic binding site around C-6). (2) In insulin treated cells (Ki = 6.11 ± 0.5 mM) and maltose (Ki = 23.5 ± 2.1 mM) are well accommodated by the site but trehalose shows no detectable inhibition. These results indicate that the site requires a specific orientation of the sugar as it approaches the transporter from the external solution. C-1 faces the inside while C-4 faces the external solution. (3) To determine the spatial and hydrogen bonding requirements for basal cells 40 μM was used as the substrate. Poor hydrogen bonding analogues and analogues with sterically hindering alkyl groups showed similar Ki values to those determined for insulin-treated cells. These results indicate that insulin does not change the specificity of the adipocyte transport system. 相似文献
11.
H.R. Bosshard M. Zürrer H. Schägger G. von Jagow 《Biochemical and biophysical research communications》1979,89(1):250-258
Cytochrome 1, the electron donor for cytochrome , is a subunit of the mitochondrial cytochrome 1 complex (complex III, cytochrome reductase). To test if cytochrome 1 is the cytochrome -binding subunit of the 1 complex, binding of cytochrome to the complex and to isolated cytochrome 1 was compared by a gel-filtration method under non-equilibrium conditions (a 1 complex lacking the Rieske ironsulfur protein was used; von Jagow et al. (1977) Biochim. Biophys. Acta , 549–558). The approximate stoichiometries and binding affinities were found to be very similar. Binding of cytochrome to isolated cytochrome which is another subunit of the reductase was not detectable by the gel-filtration method. Further, the same lysine residues of cytochrome were shielded towards chemical acetylation in the complexes 1 and 1. From this we conclude that the same surface area of cytochrome is in direct contact with cytochrome 1 and with cytochrome 1 in the respective complexes and that therefore cytochrome is most probably the structural ligand for cytochrome in mitochondrial cytochrome reductase. 相似文献
12.
A cytochrome - cytochrome oxidase complex containing 0.8–1.0 moles of cytochrome per mole of cytochrome oxidase (heme a + a3) was isolated as described by Ferguson-Miller, S., Brautigan, D.L., and Margoliash E., J. Biol. Chem. , 1104 (1976). This complex was reacted with dithiobissuccinimidyl propionate, an 11 Å bridging bifunctional reagent, and the cross-linked products obtained were analyzed by two dimensional gel electrophoresis. Cytochrome was cross-linked to subunit II of cytochrome oxidase. Other cross-linked products were formed involving different subunits of cytochrome oxidase. These included I+V, II+V, III+V, V+VII, IV+VI and IV+VII. Experiments are also described using N,N′-bis(3-succinimidyloxycarbonylpropyl) tartarate. The major product formed with this 18 Å bridging bifunctional reagent was a pair containing II+VI. 相似文献
13.
1. In mitochondrial particles antimycin binds to two separate specific sites with dissociation constants and , respectively.2. The concentrations of the two antimycin binding sites are about equal. The absolute concentration for each binding site is about 100 – 150 pmol per mg of mitochondrial protein.3. Antimycin bound to the stronger site mainly inhibits NADH- and succinate oxidase. Binding of antimycin to the weaker binding site inhibits the electron flux to exogenously added cytochrome c after blocking cytochrome oxidase by KCN.4. Under certain conditions cytochrome b and c1 are dispensible components for antimycin-sensitive electron transport.5. A model of the respiratory chain in yeast is proposed which accounts for the results reported here and previously. (Lang, B., Burger, G. and Bandlow, W. (1974) Biochim. Biophys. Acta 368, 71–85). 相似文献
14.
I C Kim 《Archives of biochemistry and biophysics》1980,203(2):519-528
Somatic (cs) and a testis-specific (ct I) cytochromes c were purified to homogeneity from rat tissues (heart, liver, kidney, and testis). The purification procedure involved (1) homogenization of tissues at pH 4.5, (2) treatment with methanol-chloroform solvents, (3) hydroxylapatite column chromatography, (4) carboxymethyl-cellulose column chromatography, and (5) Sephacryl S-200 gel filtration. The isolated cytochromes c were free from polymeric and other “modified” forms, and did not bind CO, azide, or cyanide. The absorption maxima and the molecular weights of both cytochromes cs and ct I were identical. The ratio of for cytochromes cs averaged 1.28. The unique properties of cytochrome ct I, compared to somatic cytochrome c, were as follows: (1) different elution profiles from hydroxylapatite and carboxymethyl-cellulose column chromatography experiments, (2) less basic intrinsic molecular charge shown by the slow mobility in native polyacrylamide gel electrophoresis, (3) probable asymmetric molecular shape as evidenced from gel filtration experiments, (4) significantly higher millimolar extinction coefficient values (33.6 at 549.5 nm), (5) a low ratio (1.04) of , and (6) difference of about 20 amino acid residues per mole. 相似文献
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16.
G Fauque M Bruschi J Le Gall 《Biochemical and biophysical research communications》1979,86(4):1020-1029
A new c-type cytochrome containing a single heme group, cytochrome c553(550) has been purified from (Norway strain) and some of its properties have been investigated. It has an isoelectric point of 6.6 and a higher redox potential than cytochrome c3 isolated from the same bacteria. Its molecular weight was estimated to be 9,200 by gel filtration. The main absorption peaks are at 553, 522.5 and 417 nm in the reduced form and at 690, 529, 411, 357 and 280 nm in the oxidized form. The asymmetric α band of the reduced state is similar to the one reported for socalled “split α” cytochromes c. The cytochrome contains 86 amino acid residues with 5 methionine, two cysteine and two histidine residues. The N terminal sequence of Norway cytochrome c553(550) presents no evident homology with that of Hildenborough cytochrome c553. 相似文献
17.
The ubiquinone protein, QP-C, in reduced ubiquinone-cytochrome c reductase (the b?c1-III complex) shows a stable ubisemiquinone radical when the enzyme is reduced by succinate in the presence of catalytic amounts of succinate dehydrogenase and QP-S. At room temperature using EPR technique the redox titration of the b?c1-III complex in the presence of redox dyes or succinate/fumarate couple reveals that the ubisemiquinone radical has a midpoint potential of approximately +67 mV at pH 8.0. Further analysis yields E1 of +83 mV and E2 of +51 mV corresponding to () and () or other electronated forms, respectively. The equilibrium radical concentration has been found to be affected both by pH and succinate/fumarate couple. At pH 9.0 the radical shows the maximal amplitude and stability. Below pH 7.0, little radical was detected. The electron spin relaxation behavior of ubisemiquinone radical, as examined by microwave power saturation, indicates that the ubisemiquinone radical of QP-C is somewhat isolated from other paramagnetic centers. The effects of phospholipids, QP-S, and other agents on ubisemiquinone radical formation as well as the enzymatic activity of QP-C have been studied in detail. 相似文献
18.
Thyrotoxicosis can induce increases in the concentrations of the cytochromes of the inner mitochondrial membrane in rat liver. The purpose of this study was to determine whether the increase in hepatic cytochrome c concentration in thyrotoxic rats is maintained by an increase in the rate of synthesis, a decrease in the rate of degradation, or a combination of the two. The turnover of cytochrome c labeled with δ-amino [14C]levulinate was measured in the livers of thyrotoxic rats that were in steady state with respect to liver cytochrome c concentration, liver weight, and body weight. Cytochrome c concentration was increased 3.4-fold in the livers of the thyrotoxic animals. The of liver cytochrome c was 3.7 days in the thyrotoxic and 5.7 days in euthyroid animals. It was calculated that the 3.4-fold increase in cytochrome c concentration was maintained, in the face of a 63% increase in kd, by a 5.5-fold increase in synthesis rate. 相似文献
19.
W H Fuchsman C H Barlow W J Wallace W S Caughey 《Biochemical and biophysical research communications》1974,61(2):635-643
Solid dipyridine hemes which are unreactive toward oxygen lose both pyridine ligands upon heating under vacuum to give a solid which takes up O2, reversibly, one O2 per heme. Replacement of 16O2 by 18O2 reduces only infrared bands near 1660 and 1590 cm?1, frequencies near the vibrational band for gaseous O2. No FeO bands are detected. EPR spectra reveal a free radical and ferric iron; Mössbauer, NMR and infrared spectra support an iron(III) oxidation state. Limited molecular weight data indicate a dimer. Possibly two dioxygen molecules are held sandwich fashion between two porphyrins via donor-acceptor interactions, which are facilitated by electron transfer from iron(II) into the porphyrin forming a π-anion. Such O2 bonding is not found in oxy Hb and Mb or in oxyhemerythrin but may occur with cytochrome oxidase and other oxygen utilizing (or producing) heme and other proteins. 相似文献
20.
Andrew J. Thomson A.Edward Robinson Michael K. Johnson Richard Cammack K.Krishna Rao David O. Hall 《BBA》1981,637(3):423-432
Oxidation of the 8Fe ferredoxin from Clostridium pasteurianum with potassium ferricyanide, followed by purification on Sephadex G-25 and DE-23 cellulose columns, gives a protein with an intense EPR signal at g 2.01. The low-temperature magnetic circular dichroism (MCD) spectra of this species are different from those of the oxidized high-potential iron protein from Chromatium but identical with the spectra of ferredoxin II from Desulphovibrio gigas. On reduction of the ferricyanide-treated ferredoxin with sodium dithionite only a weak EPR signal with g factors of 2.05, 1.94 and 1.89 is obtained. The low-temperature MCD spectra are strongly temperature dependent with a form similar to those of dithionite-reduced D. gigas ferredoxin II. The MCD magnetization curves are dominated by a species with ground-state effective g factors of 8.0 and g⊥ 0.0, which are also similar to those determined recently by low-temperature MCD spectroscopy for D. gigas ferredoxin II. The MCD characteristics are quite different from those of dithionite-reduced ferredoxin from Cl. pasteurianum, untreated with ferricyanide. This establishes the close similarity of the iron-sulphur clusters in ferricyanide-treated Cl. pasteurianum ferredoxin and in D. gigas ferredoxin II. The latter is known to contain a single 3Fe centre, similar to that observed in ferredoxin I from Azotobacter vinelandii by X-ray crystallography. Therefore, it is concluded that the [4Fe-4S] clusters of Cl. pasteurianum ferredoxin are converted to 3Fe clusters on oxidation with ferricyanide. 相似文献