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1.
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
2.
J C Brochon P Wahl M Charlier J C Maurizot C Hélène 《Biochemical and biophysical research communications》1977,79(4):1261-1271
A new crystal form of a mitogenic lectin from pea seeds () has been obtained which is suitable for high resolution structural work. The crystals are orthorhombic, space group P212121, with unit cell dimensions: = 64.2Å, = 72. 7Å, = 108. 3Å. The asymmetric unit contains one protein molecule. 相似文献
3.
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
4.
The purpose of this report is to review the current literature on cytochrome 5 in hepatic microsomes and to draw conclusions as to its role in microsomal electron transfer pathways. For details concerning the history of cytochrome 5 the reader is reffered to reviews by C. F. Strittmatter (1) and P. Strittmatter (2). For information on the chemistry of cytochrome 5 the reader is reffered to the papers by Ozols and Strittmatter (3), Kajihara and Hagihara (4), and Ehrenberg and Bois-Poltoratsky (5). For more recent studies on the isolation and properties of detergent solubilized cytochrome 5, which contains a hydrophobic peptide enabling reincorporation into membranes, the reader is referred to references 6-12.For simplicity, this minireview is divided into four parts, reflecting areas of study on the role of cytochrome 5 in the microsomes. One major area is in fatty acid 9 desaturation. Two other areas concern cytochrome 5 involvement in cytochrome P-450 mediated mixed function oxidations. The fourth section deals with other non-cytochrome P-450 pathways in which cytochrome 5 is suggested as being a component. 相似文献
5.
A method for demonstrating proestrogens has been developed. The method involves the incubation of the potential proestrogen with liver microsomes and NADPH in the presence of rat uteri, followed by examination of the effects of metabolism of the compound on the distribution of uterine estrogen receptor (R) in the cytosol (Rc) and in the nucleus (Rn). Thus, we examined whether DDT derivatives, which possess estrogenic activity , exhibit pro-estrogenic properties . Using this method, it appears that methoxychlor is a proestrogen, since the presence of microsomal enzymatic activity is required for methoxychlor to elicit translocation of uterine Rc into the nucleus, namely, the lowering of Rc and elevation of Rn. By contrast, o,p'DDT was active in translocating Rc and did not require the presence of microsomal enzymes for activity. 相似文献
6.
Chemically formylated Met-tRNAmMet and Met-tRNAfMet species from and yeast were tested for their capacity to serve as chain-initiators in a cell-free system from . In the presence of R 17 mRNA, initiation factors and ribosomes, all four Met-tRNAs could form functional initiation complexes as measured by ribosomal binding kinetics, fMet-puromycin formation and synthesis of a dipeptide fMet-Ala. Unformylated Met-tRNAfMet from displayed significantly less activity as a peptide chain-initiator than the formylated Met-tRNAmMet species from and yeast. Although the latter tRNAs were less effective initiators than the “physiological” initiator tRNAs, the data seem to indicate that a blocked α-amino group represents the major token of identification by which Met-tRNA is admitted to function in peptide chain initiation. 相似文献
7.
Proton and 13C magnetic resonance studies are reported on the synthetic polypentapeptide of elastin, HCO-(Val(1)-Pro(2)-Gly(3)-Val(4)-Gly(5))n-Val-OMe, where n ∼- 18. Temperature and solvent dependence of peptide N chemical shift and solvent dependence of peptide carbonyl chemical shift were used to delineate these moieties preliminary to identification of secondary structure.Based on these studies it is proposed, for the organic solvents of dimethyl sulfoxide, methanol, and low-temperature trifluoroethanol, that dynamic hydrogen bonds form in order of decreasing frequency of occurrence between the Val(1)O and the Val(4) N (a β-turn), between the Gly(3) N and the Gly(5)O (an 11-atom, hydrogen-bonded ring), and a more limited interaction between the Gly(3)O and the Gly(5) N (a γ-turn).Arguments are presented that relate the conformational features proposed above to the coacervate, which is a filamentous state. 相似文献
8.
Cooperativity in ligand binding: a new graphic analysis. 总被引:16,自引:0,他引:16
When analyzing binding of ligands to macromolecules, the existence of site-site interactions complicates a straightforward interpretation of the binding parameters obtained through classical analytical methods, such as the Scatchard plot. For describing site-site interactions, we propose a new parameter, the of the receptor sites, , calculated as . Plotting as a function of fractional occupancy (), reveals that: (1) at very low occupancy a limiting high is obtained (e) (“empty sites” conformation); (2) when the fraction of sites filled increases above a certain threshold, begins to fall due to increasing site-site interactions until (3) a limiting low (f) is obtained (“filled sites” conformation). This method has been successfully applied to the negative cooperativity of insulin receptors. 相似文献
9.
Synthesis of diphtheria toxin in E. coli cell-free lysate 总被引:7,自引:0,他引:7
An cell-free lysate was used to translate RNA from nontoxinogenic C7(?), C7 infected with β tox+ corynebacteriophage, and strain PW8. De novo synthesis of toxin was detected by immune precipitation with antitoxin, ADP-ribosylation of mammalian elongation factor 2 and rabbit skin test. The results indicated that toxin is produced in the protein synthesizing system primed with RNA from cells infected with tox+ bacteriophage and is absent in systems primed with RNA from C7(?) cells. 相似文献
10.
A Rosner K M Jakob J Gressel D Sagher 《Biochemical and biophysical research communications》1975,67(1):383-391
A 0.5 × 106r RNA found in plastids of the aquatic angiosperm , is synthesized at a much higher rate than any other rapidly labeling RNA species about h after dark-grown plants are transferred to light. The pulse labeling kinetics of the 0.5 × 106r RNA after transfer to light, argue against its involvement in the biogenesis of plant rRNAs. Although poly(A) RNA is found in , poly(A) sequences are not detected in the 0.5 × 106r RNA; yet a sucrose gradient fraction which includes RNA of this r stimulates amino acid incorporation by an cell free extract more than other RNA fractions. The possible involvement of the 0.5 × 106r RNA as a chloroplast messenger is discussed. 相似文献
11.
The synthesis of the 8,12-secoprostaglandin E1 analogs and is reported. 相似文献
12.
Light-dependent H2 evolution from dithiothreitol as electron donor was observed with cell-free preparations of anaerobically adapted and from spinach chloroplasts mixed with hydrogenase. NADH substituted for dithiothreitol as electron donor only in the preparation. Dibromothymoquinone, an antagonist of plastoquinone, selectively inhibited H2 photoevolution from NADH. These results are interpreted as indicating that 3-(3,4-dichlorophenyl)-1,1-dimethyl urea insensitive H2 photoevolution by algae containing hydrogenase is due to the capability of NADH to reduce plastoquinone in the electron transport chain, and to evolve H2 by a low redox potential carrier of photosystem I. 相似文献
13.
Addition of -nitroanisole to a reaction mixture containing phenobarbital-pretreated rabbit liver microsomes brings about an increase the reoxidation rate of NADH-reduced cytochrome b5. Addition of partially purified cytochrome b5 to a solution containing microsomes results in a marked increase in both NADH- and NADPH-dependent O-demethylation of -nitroanisole. -Nitroanisole also increases the rate of NADH mediated cytochrome P-450 reduction. From these and other results described in the Discussion section, we confirm that electrons required for NADH-dependent O-demethylation of -nitroanisole is transfered from NADH to cytochrome P-450 via cytochrome b5 and that cytochrome P-450 is the enzyme which catalyzes -nitroanisole O-demethylation. 相似文献
14.
Svante Brandänge Lars Lindblom 《Biochemical and biophysical research communications》1979,91(3):991-996
The second of the two reaction steps involved in the metabolic transformation of (?)-nicotine to (?)-cotinine , the oxidation of the intermediate is mediated mainly, if not solely, by the enzyme aldehyde oxidase (EC 1.2.3.1). Of the molecular species that constitute , nicotine Δ1′(5′) iminium ion appears to serve as the substrate. The enzyme has a strong affinity for , as shown in a study on the inhibition of the oxidation of 3-(aminocarbonyl)-1-methylpyridinium chloride. This study gave a value of Ki = 6 μM; Km = 2 μM (pH 7.4). Mainly in view of this finding, “iminium oxidase” seems to be a more adequate name than “aldehyde oxidase” for this enzyme. 相似文献
15.
Oxygen inhibits CO2 fixation by mesophyll protoplast extracts of the C3 plants, and , but stimulates the pyruvate induced CO2 fixation by mesophyll protoplast extracts of the C4 plants and . The former is reversed by increased levels of bicarbonate, whereas the latter effect is independent of bicarbonate concentration. The results are consistent with the proposal that oxygen inhibits C3 photosynthesis by competing with CO2 in the RuDP carboxylase/oxygenase system. The oxygen enhancement of C4 mesophyll photosynthesis is proposed to be due to pseudocyclic electron flow supplying additional ATP for the CO2 fixation process. 相似文献
16.
is able to take up NH4+ and CH3NH3+ against concentration gradients. Uptake of CH3NH3+ is abolished by NH4+ and partially inhibited by dinitrophenol. membranes are permeabilized for NH4+ by valinomycin. These results are regarded as evidence for an ammonium translocase in membranes otherwise only slightly permeable for NH3. 相似文献
17.
Crystals of lysozyme from Streptomyces erythraeus are orthorhombic, space group P212121 with unit cell dimensions: and ; and one molecule, of molecular weight about 18,500, per asymmetric unit. 相似文献
18.
Oswald G. Baca James W. Bodley 《Biochemical and biophysical research communications》1976,70(4):1091-1096
70S ribosomes uniformly labeled with 32PO4 were subjected to varying doses of u.v. radiation and then to the combined action of the RNases A and T1. Following these treatments the ribosomal proteins were separated by trichloroacetic acid precipitation from the noncovalently attached RNA degradation fragments. Subsequent two-dimensional gel electrophoresis and autoradiography of these proteins revealed that significant 32PO4 was associated with unique ribosomal proteins, L2 was among these. 相似文献
19.
S B West W Levin D Ryan M Vore A Y Lu 《Biochemical and biophysical research communications》1974,58(2):516-522
An enzyme system in which catalyzes the NADH-dependent of 3,4-benzpyrene has been reconstituted. The essential components of this NADH-mediated are cytochrome b5, NADH-cytochrome b5 reductase, lipid, and cytochrome P-448. 相似文献
20.
Luis O. Rodriguez Sidney M. Hecht 《Biochemical and biophysical research communications》1982,104(4):1470-1476
Consistent with a recent literature report (Repine, J. E. (1981) , 1001–1003), the release of [3H]-thymine from PM-2 DNA by Fe(II)-H2O2-generated ·OH was suppressed by dimethyl sulfoxide. In contrast, DMSO did not affect [3H]-thymine release mediated by Fe(II)-bleomycin. Under aerobic conditions in the presence of -butyl phenylnitrone, Fe(II)-BLM produces an epr signal that has been presumed to arise by transfer of ·OH or from the “active complex” of bleomycin to the spin trap. Remarkably, high concentrations (80 mM) of PBN had no effect on the ability of Fe(II)-BLM to solubilize [3H]-thymine, although the ability of authentic ·OH to degrade DNA was completely suppressed under these condition. The suproxide dismutase catalyst tetrakis(4-N-methylpyridyl)porphineiron(III) also failed to suppress BLM-mediated DNA degradation. Moreover, the epr signal observed with 1.6 mM Fe(II)-BLM in the presence of 80 mM PBN was found to be much less intense than that produced by 1.6 mM Fe(II) and 290 mM H2O2, but equivalent in intensity to that obtained with 45 mM Fe(II) and exoess H2O2. We conclude that the fragmentation of DNA produced by Fe(II)-BLM can be due neither to free ·OH nor to . We suggest that DNA degradation is initiated by an “active complex” consisting of BLM, metal and oxygen that functions by abstracting H· from susceptible sites on DNA. 相似文献