Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “CARDIOLIPIN”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,207 records · Page 67Linked to original sources
PubMed1997

Phosphatidylglycerophosphate synthase from yeast.

The phospholipid cardiolipin, or diphosphatidylglycerol, is ubiquitous in eucaryotes. It is unique in structure, subcellular localization, and potential function. Because it is found predominantly in the mitochondrial inner membrane, it is an excellent marker for mitochondrial biogenesis. Cardiolipin is required for activity of several mitochondrial enzymes and possibly also for import of proteins into the mitochondrion. To understand the role of cardiolipin in these cellular events, it is necessary to characterize the enzymes of the cardiolipin pathway, as well as the genes that control the expression of these enzymes. To date, the structural genes encoding the cardiolipin biosynthetic enzymes have not been identified in any eucaryotic organism. However, considerable information is available regarding the regulation of this pathway in yeast. The activity and regulation of the first enzyme of the pathway, CDP-diacylglycerol:sn-glycerol-3-phosphate 3-phosphatidyltransferase (phosphatidylglycerophosphate (PGP) synthase, EC 2.7.8.5), has been characterized in two evolutionarily divergent yeasts, Saccharomyces cerevisiae and Schizosaccharomyces pombe. In contrast to the second and third enzymes of the pathway, this enzyme is highly regulated, both by cross-pathway control and by factors affecting mitochondrial development. PGP synthase from S. pombe (and cardiolipin synthase from S. cerevisiae) have been purified to homogeneity. The amino acid sequences of these enzymes, combined with the availability of the complete genome sequence from S. cerevisiae will simplify the cloning of these genes in the near future.

Mitochondria↗
PubMed2000

Coagulation tests and anti-phospholipid antibodies in patients positive for lupus anticoagulant.

We examined activated partial thromboplastin time, kaolin clotting time, mixing with normal plasma in kaolin clotting time, dilute Russell's viper venom time, dilute Russell's viper venom time at high lipid concentrations, anti-phospholipid antibodies, and anti-cardiolipin-beta2-glycoprotein I complex antibody in 135 patients with prolongation of activated partial thromboplastin time and diagnosed 86 patients positive for lupus anticoagulant. The sensitivity of activated partial thromboplastin time and dilute Russell's viper venom time/dilute Russell's viper venom time-high lipid concentrations ratio for lupus anticoagulant were markedly high, but the specificity of activated partial thromboplastin time for lupus anticoagulant was not markedly high. The specificity, but not the sensitivity, of kaolin clotting time-mixing with normal plasma in kaolin clotting time was markedly high. In summary, dilute Russell's viper venom time to dilute Russell's viper venom time-high lipid concentrations ratio gave high sensitivity as well as specificity, being the only assay to confirm this. Of the patients positive for lupus anticoagulant, 25% were positive for anti-phospholipid antibodies and 17% were positive for anti-cardiolipin-beta2-glycoprotein I complex antibody. Of the lupus anticoagulant-positive patients with thrombosis, 45% were positive for anti-phospholipid antibodies, 35% were positive for anti-cardiolipin-beta2-glycoprotein I complex antibody, 60% were positive for both anti-phospholipid antibodies and anti-cardiolipin-beta2-glycoprotein I complex antibody, and only 17% were negative for anti-phospholipid antibodies and anti-cardiolipin-beta2-glycoprotein I complex antibody. These findings suggest that lupus anticoagulant can be diagnosed by dilute Russell's viper venom time/dilute Russell's viper venom time-high lipid concentrations ratio, and that thrombosis in lupus anticoagulant-positive may be predictable from both anti-phospholipid antibodies and anti-cardiolipin-beta2-glycoprotein I complex antibody. Plasma tissue type plasminogen activator level in lupus anticoagulant patients was significantly increased, and plasma tissue type plasminogen activator and fibrin-D-dimer levels in lupus anticoagulant-positive patients with thrombosis were significantly higher than in those without thrombosis, suggesting that the diagnosis of thrombosis by hemostatic markers might be important in lupus anticoagulant.

Adult↗
PubMed1999

Some anticardiolipin antibodies recognize a combination of phospholipids with thrombin-modified antithrombin, complement C4b-binding protein, and lipopolysaccharide binding protein.

The standard enzyme-linked immunosorbent assay (ELISA) for anticardiolipin antibodies (ACA) detects a heterogenous group of antibodies against cardiolipin on its own, beta2-glycoprotein I (beta2GPI), and, potentially, other phospholipid-binding plasma proteins from bovine or human origin. In an attempt to identify new proteic targets of ACA, we selected 6 patients who possessed cofactor-dependent ACA but no antibody to human or bovine beta2GPI detectable in the beta2GPI-ELISA. Three of these samples proved to recognize beta2GPI in combination with cardiolipin, but not beta2GPI directly immobilized on gamma-irradiated polystyrene or agarose beads. In the other cases, the component required for ACA binding was purified from adult bovine serum or plasma by means of ammonium sulfate precipitation and chromatography on Phenyl-Sepharose, diethyl aminoethyl (DEAE)-cellulose, heparin-Ultrogel, and Sephacryl S-300 columns. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis coupled to N-terminal amino acid microsequencing identified the cofactors of patients no. 4, 5, and 6 ACA as lipopolysaccharide binding protein (LBP), complement C4b-binding protein (C4BP), and the thrombin-antithrombin (AT) complex, respectively. Adsorption of each of these cofactor preparations with cardiolipin liposomes led to suppression of ACA reactivity, concomitant with the loss of bands from SDS gels corresponding to sequenced material. Bacterial lipopolysaccharide (which forms high-affinity complexes with LBP) specifically neutralized the cofactor activity of the LBP preparation in a concentration-dependent manner. Bovine serum and plasma, as well as the C4BP preparation, optimally supported the binding of a rabbit anti-C4BP antiserum to immobilized cardiolipin. The binding of a rabbit anti-AT antiserum to solid-phase cardiolipin was sustained by the thrombin-AT preparation and bovine serum, but neither by bovine plasma nor by native AT, thus reproducing the behavior of patient no. 6 ACA. Taking advantage of the restricted recognition by the latter ACA of a cofactor from bovine origin appearing upon clotting, we studied the generation of such activity in human plasma supplemented with bovine AT or bovine prothrombin before clotting. In these conditions, patient no. 6 antibody binding to cardiolipin required the addition of bovine AT, whereas addition of bovine prothrombin alone was ineffective. We therefore concluded that those ACA targeted bovine AT once it has been modified/cleaved by thrombin. These findings underline the wide heterogeneity of ACA and the links that may exist between various coagulation pathways, inflammation and the complement system.

Acute-Phase Proteins↗
PubMed1980

Evidence of a specific complex between adriamycin and negatively-charged phospholipids.

Membrane-model systems (monolayers, small unilamellar vesicles) were used to study the interaction between adriamycin (ADM) and phospholipids. Adsorption of 3H-labeled adriamycin on different phospholipid monolayers demonstrated the specificity of adriamycin for negatively-charged phospholipids (cardiolipin, phosphatidylserine, phosphatidic acid). The stoichiometry has been found to be approx. 2 mol (1.8) adriamycin per mol cardiolipin and approx. 1 mol (0.75) adriamycin per mol phosphatidylserine and phosphatidic acid. No adsorption was detected with neutral lipids. Surface-potential measurements confirm the formation of a complex stabilized by electrostatic interactions without penetration of the drug into the lipid lipophilic phase. Some adriamycin derivatives were used to discriminate between the ionized hydrophilic and hydrophobic contributions in the complex formation. The absorption spectrum of adriamycin in the presence of cardiolipin resembles the behavior of the ADM-DNA complex. Moreover, the association constants of the two complexes are very similar (cardiolipin-ADM, 1.6 . 10(6) . M-1; ADM-DNA, 2.4 . 10(6) . M-1). To explain the high affinity of cardiolipin for adriamycin, we proposed that two essential interactions are responsible for the complex stabilization: an electrostatic interaction between the protonated amino groups of the sugar residues and the ionized phosphate residues, and an interaction between adjacent anthraquinone chromophores. These data strongly suggest competitive behavior between a membrane site and the target. Consequently, it must be assumed that the lipidic components of the cell membrane structure may be an important determinant in the behavior of adriamycin. This observation should be kept in mind in the building of new derivatives.

Calorimetry↗
PubMed1975

Polyglycerophosphatide metabolism in Escherichia coli.

When Escherichia coli B cells were labelled with [14-C] glycerol and chased, there was a marked sparing of the phosphatidyl moiety compared to the nonacylated glycerol moiety of phosphatidylglycerol. When energy-depleted cells were restored to an energy-rich medium there resulted a conversion of 32-P-labelled cardiolipin to phosphatidylglycerol, a lack of phosphatidic acid accumulation and no loss in total polyglycerophosphatide counts. In cell-free extracts, phosphatidic acid produced from 32-P-labelled cardiolipin by the action of Escherichia coli phosphalipase D, was readily recycled to form poly-glycerophosphatide. In the presence of glycerol, such extracts displayed traansphosphatidylase activity by degrading cardiolipin to phosphatidyglycerol mainly. The results as a whole indicate that the enzyme synthesizing cardiolipin together with cardiolipin-hydrolyzing phospholipase D constitute a cycle which is normally involved in the turnover of polyglycerophosphatides in Escherichia coli.

Adenosine Triphosphate↗
PubMed1995

Association of negatively-charged phospholipids with low-density lipoprotein (LDL) increases its uptake and the deposition of cholesteryl esters by macrophages.

LDL, the major carrier of cholesterol in blood, is poorly metabolized by macrophages. In contrast, macrophages can recognize and endocytose anionic phospholipids such as phosphatidylserine, phosphatidylglycerol and cardiolipin. Since macrophages can take up large amounts of these phospholipids, experiments were performed to ascertain whether pre-incubation of native LDL with negatively-charged phospholipids would enhance the metabolism of LDL by macrophages. When 125I-LDL was incubated with cardiolipin liposomes for 18 h at 37 degrees C before addition to macrophages, an approx. 40-fold increase of LDL metabolism by these cells was observed. Similar results were found when LDL was pre-incubated with phosphatidylserine or phosphatidylglycerol; however, pre-incubation of LDL with phosphatidylcholine liposomes did not lead to an increase of LDL metabolism. The macrophage uptake of LDL pre-incubated with cardiolipin was reduced to approx. 40% of control values in the presence of dextran sulfate and fucoidin, inhibitors of anionic phospholipid uptake. Cytochalasin D, an inhibitor of phagocytosis, reduced the lysosomal degradation of LDL pre-incubated with cardiolipin to approx. 10% of control values. When the LDL-cardiolipin mixture was chromatographed on agarose gel, two peaks containing LDL were observed in the elution profile: the first peak appeared at the void volume and the second peak was detected just ahead of native LDL. The LDL in both peaks was much more extensively metabolized by macrophages than was native LDL; the LDL in the first peak was metabolized at a rate that was 8 times the second peak. The results demonstrate that negatively-charged phospholipids can form a complex with LDL which facilitates its phagocytosis by macrophages.

Cardiolipins↗
PubMed2004

Anti-beta 2 glycoprotein I antibodies in centenarians.

BACKGROUND: Non-organ-specific autoantibodies are present in centenarians without evidence of autoimmune diseases but conflicting or no data on anti-phospholipid and anti-phospholipid binding proteins were reported. OBJECTIVE: To investigate the presence and antigen specificity of anti-phospholipid and anti-phospholipid binding proteins in centenarians. METHODS: Seventy-seven centenarians, 70 adult controls, 65 unselected elderly subjects, and 38 old SENIEUR volunteers were investigated. Anti-cardiolipin, anti-human beta 2 glycoprotein I, and lupus anticoagulant were detected. Antigen specificity was assayed against plates coated with anionic, neutral and cationic phospholipids and beta 2 glycoprotein I-dependence was also evaluated. RESULTS: 54.3% of the centenarians were positive for IgG and 8.6% for IgM anti-beta 2 glycoprotein I antibodies, while only 20.7% centenarians were positive for anti-cardiolipin IgG and 2.59% for IgM; none resulted positive for lupus anticoagulant. Anti-cardiolipin positive sera cross-reacted with negatively charged phospholipids and displayed decreased binding to serum-free cardiolipin-coated plates that was restored by human beta 2 glycoprotein I or fetal calf serum. CONCLUSIONS: Centenarians display high reactivity against human beta 2 glycoprotein I but low binding to the bovine molecule in the anti-cardiolipin assay. In spite of the presence of antibodies comparable to those found in patients with the anti-phospholipid syndrome, no vascular events were reported suggesting the presence of unknown protective factors and/or the lack of triggering factors.

Aged↗
PubMed2003

Phospholipid abnormalities in children with Barth syndrome.

OBJECTIVES: We sought to identify characteristic lipid abnormalities in patients with Barth syndrome (BTHS) and to correlate the lipid profile to phenotype and genotype. BACKGROUND: Barth syndrome typically includes cardiomyopathy, skeletal myopathy, neutropenia, growth retardation, and 3-methylglutaconic aciduria, and it is commonly associated with mutations in the tafazzin (TAZ) gene, whose products are homologous to phospholipid acyltransferases. However, clinical features of BTHS have also been found in patients with normal TAZ gene. METHODS: We analyzed molecular species of phospholipids in left and right ventricle, skeletal muscle, platelets, lymphoblasts, and fibroblasts from 19 children with BTHS (positive TAZ mutation), 6 children with BTHS-like syndromes (wild-type TAZ), 4 children with isolated cardiomyopathy (wild-type TAZ), and various controls. RESULTS: Cardiolipin, the specific lipid found only in mitochondria, was decreased in all tissues from BTHS patients, whereas concentrations of other phospholipids were normal. The molecular composition of cardiolipin was altered in all tissues from BTHS patients. The molecular compositions of phosphatidylcholine and phosphatidylethanolamine were altered in the heart. Cardiolipin abnormalities were only found in children with true BTHS, not in children with BTHS-like disease or with isolated cardiomyopathy. The degree of cardiolipin deficiency was tissue-specific but did not correlate with severity or specific phenotypic expression of BTHS. CONCLUSIONS: Abnormal cardiolipin is a specific diagnostic marker of cardiomyopathies caused by TAZ mutations. These mutations lead to alterations in the fatty acid composition of several phospholipids, supporting the idea that TAZ encodes a human acyltransferase.

Acyltransferases↗
PubMed1998

Cholestasis confers resistance to the rat liver mitochondrial permeability transition.

BACKGROUND & AIMS: Bile salts can cause hepatocyte death by inducing the mitochondrial permeability transition (MPT). However, the slow progression of human cholestatic liver diseases suggests that hepatocytes adapt to resist the MPT. Bcl-x, a protein, and increased mitochondrial cardiolipin, a membrane lipid, elevate the threshold for the MPT. Our aims were to determine if liver mitochondria become resistant to the MPT during cholestasis and, if so, if the resistance is mediated by Bcl-x and/or increased cardiolipin. METHODS: Hepatocytes and liver mitochondria were obtained from bile duct-ligated (BDL) rats and sham-operated rats (control). RESULTS: After addition of glycochenodeoxycholate (GCDC), the magnitude of the MPT was reduced in mitochondria from BDL rats vs. controls. Although Bcl-xL was not increased, mitochondrial cardiolipin content was significantly greater in BDL rats vs. controls. Cell viability was also increased in hepatocytes from BDL rats vs. controls after treatment with GCDC. Feeding BDL rats a fatty acid-deficient diet prevented the increase in mitochondrial cardiolipin content; mitochondria and hepatocytes from these rats were susceptible to the MPT and hepatocellular death by GCDC. CONCLUSIONS: These data suggest that an increase in mitochondria cardiolipin content occurs during cholestasis as an adaptive phenomenon to resist cell death by the MPT.

Animals↗
PubMed1990

Lipid-protein interactions in ADP-ATP carrier/egg phosphatidylcholine recombinants studied by spin-label ESR spectroscopy.

The stoichiometry and specificity of lipid-protein interaction, as well as the lipid exchange rates at the protein interface, have been determined from the electron spin resonance spectra of spin-labeled lipids in reconstituted complexes of the mitochondrial ADP-ATP carrier with egg phosphatidylcholine. With the exception of cardiolipin and phosphatidic acid, the lipids studied are found to compete for approximately 50 sites at the intramembranous surface of the protein dimer. This number of first-shell lipid sites is unusually large for a protein of this size. The specificity for the protein is in the order stearic acid approximately phosphatidic acid approximately cardiolipin greater than phosphatidylserine greater than phosphatidylglycerol approximately phosphatidylcholine, with the maximum association constant relative to phosphatidylcholine being approximately 4. The selectivity for anionic lipids was partially screened with increasing ionic strength, but to a lesser extent for cardiolipin and phosphatidic acid than for stearic acid. Only in the case of phosphatidylserine was the selectivity reduced at high ionic strength to a level close to that for phosphatidylcholine. The off rates for lipid exchange at the protein surface were independent of lipid/protein ratio and correlated in a reciprocal fashion with the different lipid selectivities, varying from 5 x 10(6) s-1 for stearic acid at low ionic strength to 2 x 10(7) s-1 for phosphatidylcholine and phosphatidylglycerol. The off rates for cardiolipin were unusually low in comparison with the observed selectivity, and indicated the existence of a special population of sites (ca. 30% of the total) for cardiolipin, at which the exchange rate was very low.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

Anionic phospholipids bind to L-selectin (but not E-selectin) at a site distinct from the carbohydrate-binding site.

It is known that L-selectin binds to glycoconjugates containing the tetrasaccharide sialyl Lewis X in a Ca2+-dependent manner. In addition, a number of other acidic oligosaccharides (for example heparin or chondroitin sulphate) or glycolipids (for example sulphatides) bind to L-selectin independent of cations. In this paper we have established that L-selectin binds to charged phospholipids, such as cardiolipin and phosphatidylserine, but not to neutral phospholipids such as phosphatidylcholine. No interaction between E-selectin and any phospholipid was observed. The interaction between L-selectin cardiolipin was inhibited by dextran sulphate, fucoidan, mannose 6-phosphate and monoclonal antibodies previously reported to block the interaction between L-selectin and its natural ligands. Analysis of the amino acid sequence of the selectins indicated that L-selectin, but no E-selectin, contains a sequence homologous to the putative cardiolipin-binding epitope found in plasma glycoprotein beta2I. Glycoprotein beta2I and a peptide corresponding to the putative cardiolipin-binding epitope in beta2I inhibited the binding of L-selectin to cardiolipin or fucoidin. Based on the binding characteristics, sequence analysis and structural modelling of L-selectin, we suggest that the amino acid sequence KKNKED (residues 84-89) is a novel site for the binding of acidic species to L-selectin. This motif is localized close to the putative carbohydrate-binding domain of L-selectin and may be a second site within the lectin domain for the interaction of leucocyte L-selectin with its natural endothelial ligands.

Amino Acid Sequence↗
PubMed2004

C-terminal lysines determine phospholipid interaction of sarcomeric mitochondrial creatine kinase.

High affinity interaction between octameric mitochondrial creatine kinase (MtCK) and the phospholipid cardiolipin in the inner mitochondrial membrane plays an important role in metabolite channeling between MtCK and inner membrane adenylate translocator, which itself is tightly bound to cardiolipin. Three C-terminal basic residues revealed as putative cardiolipin anchors in the x-ray structures of MtCK and corresponding to lysines in human sarcomeric MtCK (sMtCK) were exchanged by in vitro mutagenesis (K369A/E, K379Q/A/E, K380Q/A/E) to yield double and triple mutants. sMtCK proteins were bacterially expressed, purified to homogeneity, and verified for structural integrity by enzymatic activity, gel filtration chromatography, and CD spectroscopy. Interaction with cardiolipin and other acidic phospholipids was quantitatively analyzed by light scattering, surface plasmon resonance, and fluorescence spectroscopy. All mutant sMtCKs showed a strong decrease in vesicle cross-linking, membrane affinity, binding capacity, membrane ordering capability, and binding-induced changes in protein structure as compared with wild type. These effects did not depend on the nature of the replacing amino acid but on the number of exchanged lysines. They were moderate for Lys-379/Lys-380 double mutants but pronounced for triple mutants, with a 30-fold lower membrane affinity and an entire lack of alterations in protein structure compared with wild-type sMtCK. However, even triple mutants partially maintained an increased order of cardiolipin-containing membranes. Thus, the three C-terminal lysines determine high affinity sMtCK/cardiolipin interaction and its effects on MtCK structure, whereas low level binding and some effect on membrane fluidity depend on other structural components. These results are discussed in regard to MtCK microcompartments and evolution.

Amino Acid Sequence↗
PubMed2004

The human TAZ gene complements mitochondrial dysfunction in the yeast taz1Delta mutant. Implications for Barth syndrome.

Barth syndrome is a genetic disorder that is caused by different mutations in the TAZ gene G4.5. The yeast gene TAZ1 is highly homologous to human TAZ, and the taz1Delta mutant has phospholipid defects similar to those observed in Barth syndrome cells, including aberrant cardiolipin species and decreased cardiolipin levels. Subcellular fractionation studies revealed that Taz1p is localized exclusively in mitochondria, which supports the theory that tafazzins are involved in cardiolipin remodeling. Because cardiolipin plays an important role in respiratory function, we measured the energy transformation and osmotic properties of isolated mitochondria from the taz1Delta mutant. Energy coupling in taz1Delta mitochondria was dependent on the rate of oxidative phosphorylation, as coupling was diminished when NADH was used as a respiratory substrate but was unaffected when ethanol was the substrate. Membrane stability was compromised in taz1Delta mitochondria exposed to increased temperature and hypotonic conditions. Mitochondria from taz1Delta also displayed decreased swelling in response to ATP, which induces the yeast mitochondrial unspecific channel, and to alamethicin, a membrane-disrupting agent. Coupling was measured in taz1Delta cells containing different splice variants of the human TAZ gene. Only the variant that restores wild type cardiolipin synthesis (lacking exon 5) restored coupling in hypotonic conditions and at elevated temperature. These findings may shed light on the mitochondrial deficiencies observed in Barth syndrome.

Acyltransferases↗
PubMed1991

The H3 anti-phospholipid idiotype is found in patients with systemic lupus erythematosus (SLE) but not in patients with syphilis.

The human H3 idiotype, defined by a mouse monoclonal antibody S2.9, is commonly found in patients with SLE where it is correlated with the amount of anti-cardiolipin antibodies. No correlation between the amount of anti-cardiolipin antibody and the H3 idiotype is found in patients with syphilis. Using the S2.9 antibody, serum from each of 10 patients with SLE and eight patients with syphilis was separated into H3-bearing and H3-negative fractions. Comparison of the partition of anti-cardiolipin antibody in these two groups of patients revealed that much of the anti-cardiolipin antibody (44-91%) was found in the H3+ fraction in patients with SLE; in patients with syphilis, virtually none of the anti-cardiolipin antibody was H3+. In patients with SLE, the H3+ fraction contained both IgG and IgM and antibodies of both kappa and lambda light chains. The H3+ fraction was polyspecific and frequently reacted with dsDNA.

Antibody Specificity↗
PubMed1994

Histones interact with anionic phospholipids with high avidity; its relevance for the binding of histone-antihistone immune complexes.

Antibodies recognizing anionic phospholipids have been described in systemic lupus erythematosus (SLE) and other autoimmune diseases. Recent studies have shown that some of these antibodies may recognize a cardiolipin-binding protein (apolipoprotein H) rather than phospholipids. A similar possibility is conceivable for other cardiolipin-binding proteins that are targets of autoantibodies. In this study we have addressed whether this might be the case for histones, a set of highly cationic and widely distributed proteins that react in a well known autoantibody system. Our results indicate that: (i) histones bind to anionic phospholipids (cardiolipin and phosphatidylserine) with high avidity, but not to zwitterionic phospholipids (phosphatidylcholine); (ii) monoclonal and polyclonal antihistone antibodies recognize histones bound to cardiolipin; (iii) the addition of histones to serum samples containing antihistone antibodies often enhances their anticardiolipin reactivity. In addition, we have found that antihistone-producing hybridomas derived from MRL-lpr mice may show anticardiolipin activity due to the presence of histones in the cell culture supernatants with the resultant formation of immune complexes. Taken together, the results suggest a potential role for histones in the anti-cardiolipin activity detected in sera containing antihistone antibodies. These histone-phospholipid interactions should be taken into account when evaluating the pathogenic effects of antihistone antibodies or other autoantibodies reacting with nuclear components (e.g. nucleosomes) containing histones.

Animals↗
PubMed1977

The interaction of phospholipid membranes and detergents with glutamate dehydrogenase.

1. The interaction of beef liver glutamate dehydrogenase with cardiolipin from both beef liver mitochondria and beef heart mitochondria, with phosphatidylcholine from both beef liver mitochondria and egg-yolk, and with beef brain phosphatidylserine was investigated by steady-state kinetic methods. 2. the phosphatidylcholine did not inhibit the enzyme under a wide range of conditions. The cardiolipins and phosphatidylserine inhibited the enzyme. The inhibition by these lipids was found to diminish with time if the lipids were prepared and the reaction was studied in either phosphate or Tris buffers, but in zwitterionic buffers these lipid brought about a rapid, reversible inhibition which remained stable with time for at least 150 min. 3. The kinetic type of the inhibition was difficult to determine because of variation between lipid sonicates. Complex mixed types of inhibition were found with cardiolipin, and with phosphatidylserine the inhibition approximated to a non-competitive interaction with Ki(app) values varying between (0.9-6.1) x 10(-6)M. 4. The extent of inhibition decreased with increasing pH and with increasing ionic strength. Basic proteins, such as cytochrome c, show a higher affinity for the anionic membranes and can dissociate the enzyme-lipid complexes. Cosonicates of the cardiolipin and phosphatidylcholine inhibited the enzyme, the extent of inhibition increasing in proportion to the amount of acidic lipid. 5. Sodium dodecylsulphate causes a time-dependent inhibition of the enzyme. The kinetics of this effect and its variation with detergent concentration were studied. 6. The relationship of these observations to the structure and function of the enzyme is discussed. It is suggested that their apparent regulation of the enzyme by oestrogens and other small molecules is due to their binding in vitro at sites on the enzyme designed for binding cardiolipin, when the enzyme is functioning in vivo. The association of the enzyme oligomer in vitro may, for similar reasons, be an artifact.

Animals↗
PubMed1992

Interactions of phospholipids with the mitochondrial cytochrome-c reductase studied by spin-label ESR and NMR spectroscopy.

Protein/phospholipid interactions in the solubilized mitochondrial ubihydroquinone:cytochrome-c oxidoreductase (bc1 complex) were studied by spin-label electron-spin resonance and by 31P-NMR spectroscopy. Spin-labelled phospholipids were employed to probe the relative binding affinities of a number of phospholipids with regard to the significance of phospholipids for the activity and stability of this multisubunit complex. The protein was titrated with spin-labelled cardiolipin (1,3-bisphosphatidyl-sn-glycerol) and with the spin-labelled analogues of PtdCho and PtdEtn, both of which have been shown recently to elicit a substantial increase in electron-transport activity [Schägger, H., Hagen, T., Roth, B., Brandt, U., Link, T. A. & von Jagow, G. (1990) Eur. J. Biochem. 190, 123-130]. A simplified distribution model showed that neutral phospholipids have much lower protein affinity than cardiolipin. In contrast to the transient weak lipid binding detected by spin-label electron-spin resonance, 31P NMR revealed a tightly bound cardiolipin portion, even after careful delipidation of the complex. Considerable line narrowing was observed after phospholipase A2 digestion of the bound cardiolipin, whereas addition of SDS resulted in complete release. Relative proportions and line widths of mobile and immobilized lipids were obtained by deconvoluting the partially overlapping signals. The current results are discussed with reference to similar findings with other mitochondrial membrane proteins. It is assumed that activation by neutral phospholipids reflects a generalized effect on the protein conformation. Cardiolipin binding is believed to be important for the structural integrity of the mitochondrial protein complexes.

Animals↗
PubMed1987

Enzyme-linked immunosorbent assay for detection of antibodies to the venereal disease research laboratory (VDRL) antigen in syphilis.

An enzyme-linked immunosorbent assay (ELISA) for detection of immunoglobulin G (IgG) and IgM to cardiolipin, lecithin, and cholesterol (VDRL [Venereal Disease Research Laboratory] ELISA) is described. The specificity of the VDRL ELISA for IgG and IgM was 99.6 and 99.5%, respectively, with sera from 1,008 persons without syphilis. For a group of patients with false-positive results in traditional nontreponemal tests and for patients with autoimmune diseases, the VDRL ELISA for IgG had a higher specificity than the VDRL ELISA for IgM. The sensitivity for IgG and IgM with 118 sera from patients with untreated syphilis was 96.6 and 94.9%, respectively, which was equivalent to the sensitivities of the traditional nontreponemal tests. The performance of the VDRL ELISA was compared with that of an ELISA that uses cardiolipin as the antigen (cardiolipin ELISA). The VDRL ELISA was significantly more sensitive (P less than or equal to 0.01) than the cardiolipin ELISA with 25 sera from syphilis patients but was less sensitive (P less than or equal to 0.01) with 53 sera from patients with autoimmune diseases. The antibody reactivity in the VDRL ELISA could not be absorbed out by lecithin and cholesterol, and the sera from patients with syphilis did not react in an ELISA that uses cholesterol and lecithin as the antigen. This indicates that cholesterol and lecithin, although not antigenic by themselves, may change the structural form of the epitope on cardiolipin so that it becomes more recognizable for antibodies in syphilis and less recognizable for antibodies in autoimmune diseases. The results of the VDRL ELISA were expressed in percentages of the absorbance value of a positive control. The VDRL ELISA gave, without titration of sera, quantitative results that correlated with the quantitative results of the traditional nontreponemal tests obtained by titration. The VDRL ELISA will be well suited for large-scale testing for syphilis and may replace other nontreponemal tests.

Antibodies, Bacterial↗