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PubMedDate not supplied

[Properties of polysaccharide complexes produced by Azospirillum brasilense and polysaccharides isolated from these complexes].

Azospirillum brasilense strains Sp7, Sp7 (S-form), Sp107, Sp245, Sp246, S17, and 15 when cultivated in a liquid synthetic malate medium up to the end of the logarithmic phase of growth were shown to produce at least two complex polysaccharide-containing components. The components were arbitrarily called lipopolysaccharide-protein complex (LPPC) and polysaccharide-lipid complex (PSLC). The LPPCs and PSLCs from the strains Sp7, Sp107, Sp245, Sp246, and S17 were shown to interact with a wheat germ agglutinin (WGA). From PSLCs, acidic polysaccharides (PS) were isolated and their specific rotation, molecular masses, affinity for WGA, and monosaccharide composition were determined. The PSs of all strains contained rhamnose, galacturonic acid, and galactose (except the strain Sp246), and glucosamine (except the strain Sp7 (S-form)), while the PSs of the strains Sp7 and S17 also contained fucose and mannose, respectively. It is suggested that LPPCs and PSLCs may be involved in the process of interaction of azospirilla with wheat root surfaces, and that PSsare probably active parts of the LPPCs and PSLCs. The ability of LPPCs and PSs to interact with Congo red in aqueous solutions was investigated.

Azospirillum brasilense↗

PubMed1994

Effects of Cu(II) complexes on photosynthesis in spinach chloroplasts. Aqua(aryloxyacetato)copper(II) complexes.

The inhibitory effect of 14 aqua(aryloxyacetato) copper(II) complexes on oxygen evolution rate in spinach chloroplasts has been investigated. The inhibitory effect of these effectors on photosynthesis was confirmed by Hill reaction as well as by EPR and fluorescence spectroscopies. The results of the EPR study showed that the sites of action of the studied effectors are Z+ and Y+ intermediates at the donor side of the photosystem (PS) 2. The EPR study also showed that another site of action is the oxygen evolving complex, namely its manganese cluster. The above suggestions were supported by the results of the fluorescence study as well. Based on the restoring of the photosynthetic electron transport to 2,6-dichlorophenol-indophenol in chloroplasts inhibited by the studied Cu(II) complexes using sym-diphenylcarbazide it can be assumed that the own core of PS2 (P680) and a part of the electron transport chain-at least up to plastoquinone-remain intact.

Chloroplasts↗

PubMed1994

Thrombin-Hirudin complex formation, thrombin-antithrombin III complex formation, and thrombin generation after intrinsic activation of plasma.

To investigate the relative importance of direct inhibition of thrombin by complex formation and of inhibition of thrombin generation to the mechanisms by that unfractionated heparin (UH) and recombinant hirudin (rH) exert their anticoagulant effects, thrombin-antithrombin III complex (TAT) and thrombin-hirudin complex (THC) formation was compared with the generation of thrombin and prothrombin fragments 1 + 2 (F 1 + 2). Clotting was initiated by activation of citrated plasma in the absence or presence of UH or rH using partial thromboplastin, ellagic acid and calcium chloride. THC was determined by means of ELISA using specific antibodies to thrombin and rH. Activation of citrated plasma resulted in a sudden onset of thrombin generation after a lag phase of 2 min. Addition of 50 ng rH/ml plasma or 0.1 UH/ml plasma prolonged the clotting time to 3 min. While the peak of thrombin was only slightly decreased in hirudinized plasma, in heparinized plasma thrombin generation was significantly lower than in not anticoagulated plasma. This difference was more pronounced when the lag phase was prolonged to 5 min using 400 ng rH/ml plasma or 0.35 U UH/ml plasma. Using 1200 ng rH/ml or 0.65 U UH/ml to obtain a clotting time of 9 min only a small amount of thrombin could be detected in heparinized plasma, but hirudinized plasma still showed a high peak of thrombin. F 1 + 2 showed essentially the same pattern as thrombin. Prior to the onset of visible clot formation in all experiments using different concentrations of UH about the same values of TAT were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Antithrombin III↗

PubMedDate not supplied

[Circular dichroism of DNA complexes with dyes. III. Effect of latent optical activity and the structure of the complexes].

Circular dichroism anisotropy was studied both theoretically and experimentally for the complexes of DNA and dsRNA with dyes (proflavine, 2,7-di-t-butyl proflavine, "Hoechst-33258") and antibiotics (distamycin A, netropsin and olivomycin). Theoretical analysis showed that general features of CD anisotropy, revealed in the previous studies (CD components--delta epsilon parallel to and delta epsilon perpendicular--are ten times or more bigger than the CD-effect without orientation, and delta epsilon parallel to approximately 2 delta epsilon perpendicular) are due to the existence of a specific effect named "latent" optical activity (LOA). This effect can be observed in many cases of non-chiral symmetrical chromophores if they are oriented. The effect is due to the excitation of an electrical dipole transition and a perpendicular magnetic dipole transition (or quadrupole transition) of a molecule. The amplitude and the sign of the LOA-effect depends on the orientation of the chromophores with respect to the light beam; with a random orientation the mutual compensation of LOA-effects of different chromophores happens and no LOA-effect appears. The analitycal expressions relating the value of LOA-effect of the system with electronical characteristics of the chromophores and the geometrical parametra of their arrangement was obtained. The experimental data obtained for the oriented complexes of DNA and dsRNA with proflavine made it possible to determine an angle between the chromophore and the plane perpendicular to the DNA axis--gamma. For the calf thymus DNA gamma = = + 1.8 +/- 0.4 degrees, for the phage T2 DNA gamma = + 2.2 +/- 0.4 degrees, and for phage f2 dsRNA gamma=--3.5 +/- +/- 0.5 degrees. These results, obtained at relatively low concentrations of the bound proflavine (r approximately 0.01), are in accordance with the intercalating mode of the dye binding. A study of CD anisotropy of DNA complexes with other ligands showed that many different chromophores possess LOA-effect. This phenomenon can be used to obtain both spectroscopic and structural information about the systems similar to those reported here.

Acridines↗

PubMed1995

Isolation and characterization of a Photosystem II complex from the red alga Cyanidium caldarium: association of cytochrome c-550 and a 12 kDa protein with the complex.

A Photosystem II (PS II) complex was purified from an acidophilic as well as a thermophilic red alga, Cyanidium caldarium. The purified PS II complex was essentially devoid of phycobiliproteins and other contaminating components, and showed a high oxygen-evolving activity of 2375 mumol O2/mg Chl per h using phenyl-p-benzoquinone as the electron acceptor. The expression of this high activity did not require addition of exogenous Ca2+, although EDTA reduced the activity by 40%. This effect of EDTA can be reversed not only by Ca2+ but also by Mg2+; a similar Mg2+ effect has been observed in purified cyanobacterial PS II but not in higher plant PS II. Immunoblotting analysis indicated the presence of major intrinsic polypeptides commonly found in PS II from cyanobacteria and higher plants as well as the extrinsic 33 kDa protein. Antibodies against the extrinsic 23 and 17 kDa proteins of higher plant PS II, however, did not crossreact with any polypeptides in the purified PS II, indicating the absence of these proteins in the red alga. In contrast, two other extrinsic proteins of 17 and 12 kDa were present in the red algal PS II; they were released by 1 M Tris or Urea/NaCl treatment but not by 1 M NaCl. The 17 kDa polypeptide was identified to be cytochrome c-550 from heme-staining, immunoblot analysis and N-terminal amino acid sequencing, and the 12 kDa protein was found to be homologous to the 12 kDa extrinsic protein of cyanobacterial PS II from its N-terminal sequence. These results indicate that PS II from the red alga is closely related to PS II from cyanobacteria rather than to that from higher plants, and that the replacement of PS II extrinsic cytochrome c-550 and the 12 kDa protein by the extrinsic 23 and 17 kDa proteins occurred during evolution from red algae to green algae and higher plants.

Amino Acid Sequence↗

PubMed1988

Mobile sequences in the pyruvate dehydrogenase complex, the E2 component, the catalytic domain and the 2-oxoglutarate dehydrogenase complex of Azotobacter vinelandii, as detected by 600 MHz 1H-NMR spectroscopy.

600 MHz 1H-NMR spectroscopy demonstrates that the pyruvate dehydrogenase complex of Azotobacter vinelandii contains regions of the polypeptide chain with intramolecular mobility. This mobility is located in the E2 component and can probably be ascribed to alanine-proline-rich regions that link the lipoyl subdomains to each other as well as to the E1 and E3 binding domain. In the catalytic domain of E2, which is thought to form a compact, rigid core, also conformational flexibility is observed. It is conceivable that the N-terminal region of the catalytic domain, which contains many alanine residues, is responsible for the observed mobility. In the low-field region of the 1H-NMR spectrum of E2 specific resonances are found, which can be ascribed to mobile phenylalanine, histidine and/or tyrosine residues which are located in the E1 and E3 binding domain that links the lipoyl domain to the catalytic domain. In the 1H-NMR spectrum of the intact complex, these resonances cannot be observed, indicating a decreased mobility of the E1 and E3 binding domain.

Acetyltransferases↗

PubMed1991

Identities of four low-molecular-mass subunits of the photosystem I complex from Anabaena variabilis ATCC 29413. Evidence for the presence of the psaI gene product in a cyanobacterial complex.

Photosystem I (PSI) complex of Anabaena variabilis ATCC 29413 consists of at least 11 subunits, 9 of which are resolved by high resolution gel electrophoresis. N-terminal amino acid sequences of the four subunits with molecular masses of 6.8, 5.2, 4.8 and 3.5 kDa were determined. Based on the sequence homology, the 3.5 kDa subunit was revealed to correspond to PSI-I (the gene product of psaI), which had so far been detected only in higher plant PSI complexes. The 6.8 kDa protein and 4.8 kDa protein were identified as gene products of psaK and psaJ, respectively. The 5.2 kDa protein was homologous to a 4.8 kDa subunit of PSI of the thermophilic cyanobacterium Synechococcus vulcanus, suggesting that this protein is a component of PSI in cyanobacteria.

Amino Acid Sequence↗

PubMed1984

Comparison of pathologic and normal sera by immune complex determination: five disease groups within 190 samples are discriminated by computer-selected combinations of 13 methods. Report of the Italian committee for the study of immune complexes (WIC).

Pathological (190) and normal (33) sera were tested for their content of circulating immune complexes (CIC) by a battery of 13 assays performed in 11 laboratories. Statistical processing was done both by pooling all pathological samples and by extracting those falling into well-defined disease groups, i.e., rheumatoid arthritis, diabetes, lupus, melanoma, and glomerulonephritis. Highly significant correlations between methods--taken two at a time--for each disease differed in proportion (ranging from 6 to 30%) and in the pattern displayed on a checkerboard. Disease-linked patterns were also found when a function maximizing discrimination between pathological and normal samples was derived by combining the information from all methods. Here the order and the weight attributed by the computer to the methods differed for each of the disease groups. Taken together these results are interpreted as an indication that all assays may not determine the same classes of CIC, and thus vary in sensitivity depending on the prevailing properties of the complexes present in the serum, which in turn may depend on the etiology, pathogenesis, and stage of the disease.

Antigen-Antibody Complex↗

PubMed2000

Analyzing your complexes: structure of the quinol-fumarate reductase respiratory complex.

The integral membrane protein complex quinol-fumarate reductase catalyzes the terminal step of a major anaerobic respiratory pathway. The homologous enzyme succinate-quinone oxidoreductase participates in aerobic respiration both as complex II and as a member of the Krebs cycle. Last year, two structures of quinol-fumarate reductases were reported. These structures revealed the cofactor organization linking the fumarate and quinol sites, and showed a cofactor arrangement across the membrane that is suggestive of a possible energy coupling function.

Animals↗

PubMed2003

Effects of thyroid state on H2O2 production by rat heart mitochondria: sites of production with complex I- and complex II-linked substrates.

This work was designed to determine possible effects of altered thyroid states on rates and sites of H 2 O 2 production by rat heart mitochondria. Rates of O 2 consumption and H 2 O 2 release, capacities to remove the peroxide, lipid peroxidation, cytochrome oxidase activities and ubiquinone levels were determined in heart mitochondria from euthyroid, hypothyroid, and hyperthyroid rats. Hypothyroidism decreased, whereas hyperthyroidism increased the rates of O 2 consumption and H 2 O 2 release during both state 4 and state 3 respiration with Complex I- or Complex II-linked substrates. The percentage of O 2 released as H 2 O 2 was not significantly affected by thyroid state. However, the mitochondrial capacity to remove H 2 O 2 increased in the transition from hypothyroid to hyperthyroid state, which indicates that H 2 O 2 production did not modify in proportion to the rate of O 2 consumption. The thyroid-state-linked changes in H 2 O 2 production were well correlated with the levels of hydroperoxides. Rates of H 2 O 2 release in the presence of respiratory inhibitors indicated that changes in the H 2 O 2 production occurred at both sites at which H 2 O 2 was generated in euthyroid state. This result and the observation that ubiquinol levels and cytochrome oxidase activities increase in the transition from hypothyroid to hyperthyroid state suggest that the modifications of H 2 O 2 production are due to a modulation by thyroid hormone of mitochondrial content of autoxidisable electron carriers.

Animals↗

PubMed1984

Sequence homology and structural similarity between cytochrome b of mitochondrial complex III and the chloroplast b6-f complex: position of the cytochrome b hemes in the membrane.

The amino acid sequences of cytochrome b of complex III from five different mitochondrial sources (human, bovine, mouse, yeast, and Aspergillus nidulans) and the chloroplast cytochrome b6 from spinach show a high degree of homology. Calculation of the distribution of hydrophobic residues with a "hydropathy" function that is conserved in this family of proteins implies that the membrane-folding pattern of the 42-kilodalton (kDa) mitochondrial cytochromes involves 8-9 membrane-spanning domains. The smaller 23-kDa chloroplast cytochrome appears to fold in five spanning domains that are similar to the first five of the mitochondria. Four highly conserved histidines are considered to be the likely ligands for the two hemes. The positions of the histidines along the spanning segments and in a cross section of the membrane-spanning alpha helices implies that two ligand pairs, His-82-His-197/198 and His-96-His-183, bridge the spanning peptides II and V, and the two hemes reside on opposite sides of the hydrophobic membrane core. In addition, the 17-kDa protein of the chloroplast b6-f complex appears to contain one or more of the functions of the COOH-terminal end of the mitochondrial cytochrome b polypeptide.

Amino Acid Sequence↗

PubMed1989

Complement-mediated endothelial cell damage in immune complex vasculitis of the skin: ultrastructural localization of the membrane attack complex.

Activation of the complement system is an important element in our concept of the pathomechanism of immune complex (IC) vasculitis. Both deposition of IC and attraction of polymorphonuclear leukocytes (PMN) are effected by products of complement activation. Actual tissue damage, however, is believed to be caused by PMN penetrating the vessel wall. Our former finding that deposits of membrane attack complex of complement (MAC) are found predominantly in skin lesions of patients with IC vasculitis and not in perilesional skin, has raised the question whether the complement system itself (by way of the MAC) contributes to tissue damage. Our present study shows the ultrastructural localization of MAC in lesional and clinically uninvolved skin in two patients with a cutaneous IC vasculitis. Lesional skin deposits of MAC were found on endothelial cells (EC) of upper dermal vessels and on infiltrating PMN. Uninvolved skin deposits of MAC were found on some EC, but clearly to a lesser extent than on EC of the lesional skin. In the skin of two healthy controls MAC was only found sporadically on EC. Deposits of MAC on EC in the lesional skin were often associated with a typical form of local cell swelling. This local form of endothelial cell swelling was incidentally seen in vessels of clinically uninvolved skin, but not in the skin of the two controls. The association of the endothelial cell swelling with deposits of MAC suggests that the complement system can have a direct damaging effect on EC in IC vasculitis by the assembly of MAC on the endothelial cell membrane.

Aged↗

PubMed2004

BDNF increases rat brain mitochondrial respiratory coupling at complex I, but not complex II.

Brain-derived neurotrophic factor (BDNF) governs both the selective survival of neurons during development and the experience-based regulation of synaptic strength throughout life. BDNF produced a concentration-dependent increase in the respiratory control index (RCI, a measure of the efficiency of respiratory coupling, ATP synthesis and organelle integrity) of rat brain mitochondria. This effect was mediated via a MAP kinase pathway and highly specific for oxidation of glutamate plus malate (complex I) by brain mitochondria. The oxidation by brain mitochondria of the complex II substrate succinate was unaffected by BDNF. The failure of BDNF to modify respiratory activity associated with mitochondrial preparations isolated from rat liver indicates that the actions of the neurotrophin are tissue specific. BDNF also increased the RCI values associated with Ca2+ -induced respiration to a similar extent. This is the first demonstration that BDNF, in addition to modifying neuronal plasticity, can modify brain metabolism and the efficiency of oxygen utilization. The finding that neurotrophins can alter mitochondrial oxidative efficiency has important implications for neurodegenerative and psychiatric diseases.

Animals↗

PubMed1989

Regulation of the mitochondrial multienzyme complexes in complex metabolic systems.

During the past two decades, I and the members of my laboratory have enjoyed very much contributing to the body of knowledge concerning the alpha-keto acid dehydrogenase complexes. We would hope that some of our work has allowed those interested in this area a perception as to how these interesting enzyme complexes are regulated in intact metabolic systems. And last, but certainly not least, I have treasured both my professional relationship and my personal friendship with Lester Reed. His work and his presence in this field of inquiry serve as a gold standard for all of us.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗

PubMed1979

Experimental chronic serum sickness in rats. A model of immune complex glomerulonephritis and systemic immune complex deposition.

This article describes a method of immunization that produces chronic serum sickness in rats within a relatively short time. Fisher rats, which were immunized subcutaneously three times with bovine serum albumin (BSA) in adjuvant, responded with high titers of antibodies to BSA. 2 weeks after the third subcutaneous immunization, daily increasing amounts of BSA were injected either intraperitoneally or intravenously. When an intravenous dose of 2mg of BSA was reached, the rats were given daily intravenous injections of BSA for several weeks. This procedure, which avoided death from anaphylaxis, induced severe proliferative glomerulonephritis in all the rats and produced deposition of antigen-antibody complexes in many other organs besides the kidney. This highly reproducible model of experimental chronic serum sickness in inbred animals may have applications for the study of the mechanisms of immune complex disease.

Animals↗

PubMed1987

The effect of rheumatoid factor on the clearance of endogenous immune complexes formed in low-affinity mice during the induction of immune complex disease.

Intravenous injection of rheumatoid factor (RF) had a marked effect on the clearance kinetics of immune complexes (IC) formed in vivo during induction of chronic immune complex disease in low-affinity mice. RF resulted in a significant increase in IC level and clearance time in 64% of mice with circulating IC after antigen injection, suggesting that RF may alter the handling of potentially pathogenic IC which localize in the renal capillaries causing glomerulonephritis.

Animals↗

PubMed1987

IgM, IgG and IgA rheumatoid factors and circulating immune complexes in patients with AIDS and AIDS-related complex with serological abnormalities.

To investigate some humoral aspects which may reflect the involvement of B lymphocytes in the acquired immunodeficiency syndrome (AIDS), we used an enzyme-linked immunoassay (ELISA) to determine the levels of IgM, IgG and IgA rheumatoid factors (RF) in 16 patients suffering from full-blown AIDS and 32 patients with AIDS-related complex (ARC), in the clinical form of lymphoadenopathy syndrome (LAS), compared with 40 healthy, young heterosexual subjects. Both AIDS and ARC patients showed a greater incidence of high IgM RF levels, with mean values significantly higher than controls, but with no differences between the two pathological groups. IgG RF behaviour was similar in the two patient populations and the healthy subjects. IgA RF were significantly raised in AIDS and ARC. Further information on RF was obtained by determination of the immunoglobulin levels of the respective isotypes in the same patients. Mean IgG levels were above normal in AIDS and ARC patients, but the latter group showed a higher incidence of increased values and higher mean levels. The IgA isotype was significantly increased mainly in AIDS patients. The behaviour of IgM was virtually the same in the three groups studied. A difference between AIDS and ARC patients was established by the detection of circulating immune-complexes (IC) by the C1q-binding and CIC-conglutinin assays. IC were significantly high, by both methods, only in the ARC group, but normal or very low in AIDS. These overall findings suggest once again the impairment of B cell function in AIDS, with prevalent hyperactivation in ARC and exhaustion in full-blown AIDS, and apparent preservation, in the latter group, of the antibody responses which are more closely related to the activity of subsets of T helper cells.

AIDS-Related Complex↗

PubMed1989

Hydatid disease: analysis of parasite antigens in circulating immune complexes and in preformed hydatid antigen-antibody complexes.

Fifty-three sera from 29 patients with hydatid disease, all but one positive for specific anti-parasite antibodies and all negative for specific circulating antigens, were studied for the presence of circulating immune complexes (CIC) by conglutinin binding-assay (KgBA). Fourteen serum samples (26%) from eight patients (27%) were positive. These positive sera were pooled for each patient and the eight samples were PEG-precipitated and analysed for the presence of specific Echinococcus granulosus antigens in the CIC using a human anti-human-hydatid cyst fluid antiserum capable of recognizing the major antigenic systems of the parasite namely, antigens 4 and 5. The assays utilized for detecting antigen in CIC were: (a) blotting on nitrocellulose paper after sodium dodecil sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and specific immunological detection; (b) ultracentrifugation in acid buffer and subsequent detection of antigens by a sandwich-radioimmuno assay (RIA); (c) protein separation by isoelectric focusing (IEF) and specific immunological recognition. In addition, all positive sera were analysed for the presence of antigen in the CIC by a modified KgBA and by polyethylenglicol (PEG)-precipitation in acid buffer followed by immunological recognition of antigen. All tests gave negative results with the patients' samples, but were positive with preformed in vitro complexes between parasite antigens and corresponding antibodies. Failure to detect antigen in the CIC could be due to: 1) insufficient sensitivity of the assays used to detect hydatid antigens in CIC; 2) rapid clearance of antigen or CIC from the circulation; 3) presence of parasite antigen not recognized by the antiserum employed; 4) production of CIC as a result of polyclonal B-cell activation. This last hypothesis is supported by the demonstration of IgM-rheumatoid factor (RF) and anti-F(ab')2 antibodies respectively in 11 (44%) and 13 (52%) out of 25 patients.

Animals↗