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J Leunissen-Bijvelt

Publications and source records attributed to J Leunissen-Bijvelt.

18 recordsLinked to original sources
PubMed1988

Accumulation of LamB-LacZ hybrid proteins in intracytoplasmic membrane-like structures in Escherichia coli K12.

The subcellular location of LamB-LacZ hybrid proteins in the Escherichia coli K12 strains pop3234 and pop3299 was investigated by immunocytochemical detection and protease-accessibility experiments. Induction of the synthesis of the hybrid proteins resulted in the appearance of membrane-like structures within the cytoplasm of the cells. Labelling of ultrathin cryosections of the cells with anti-beta-galactosidase or anti-LamB protein serum and protein-A-gold complexes revealed that the hybrid proteins were associated with these membrane-like structures or accumulated within the cytoplasm. Protease-accessibility experiments confirmed this localization. Moreover, when low quantities of hybrid proteins were produced, i.e. in uninduced pop3234 cells or in induced pop3299 cells, the hybrid proteins were accessible to trypsin from the periplasmic side of the inner membrane, leaving protected fragments with an apparent Mr of 83,000. Apparently, these hybrid proteins are partly translocated through the inner membrane, resulting in membrane-spanning forms of the proteins.

Bacterial Outer Membrane Proteins↗
PubMed1987

Gramicidin-induced hexagonal HII phase formation in erythrocyte membranes.

Using 31P nuclear magnetic resonance (NMR), small-angle X-ray scattering (SAXS), and freeze-fracture electron microscopic (FFEM) techniques, it is shown that gramicidin induces a hexagonal HII phase not only in liposomes prepared from total lipids extracted from human erythrocytes but also in isolated human erythrocyte membranes (white ghosts). A 37 degrees C, HII phase formation is detected at a gramicidin to phospholipid molar ratio exceeding 1:80. At a molar ratio of 1:5, about 30% of the phospholipid is organized in the HII phase. The gramicidin-induced HII phase exhibits a very small 31P chemical shift anisotropy [(CSA) approximately 10 +/- 1 ppm], indicating decreased head-group order, and it displays a temperature-dependent increase in tube diameter from 60.2 A at 4 degrees C to 64.2 A at 37 degrees C in ghosts and from 62.8 to 69.4 A at 37 degrees C in total lipid extracts, both in the presence of 1 mol of gramicidin/10 mol of phospholipid. This anomalous temperature-dependent behavior is probably due to the presence of cholesterol. 31P NMR data indicate that the HII phase formation by gramicidin is temperature dependent and show the gradual disappearance of the HII phase at low temperatures (less than 20 degrees C), resulting in a bilayer type of 31P NMR line shape at 4 degrees C, whereas SAXS and FFEM data suggest equal amounts of HII phases at all temperatures. This apparent discrepancy is probably the result of a decrease in the rate of lateral diffusion of the membrane phospholipids which leads to incomplete averaging of the 31P CSA in the HII phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Erythrocyte Membrane↗
PubMed1987

Interaction of melittin with negatively charged phospholipids: consequences for lipid organization.

A characterization of the structural alterations induced by melittin in model-membranes of dioleoylphosphatidic acid and egg phosphatidylglycerol is presented, based on the use of 31P-NMR, freeze-fracture electron microscopy and small angle X-ray scattering. In accordance with earlier findings on the cardiolipin-melittin system, melittin is found to have an inverted phase inducing effect on these negatively charged lipids, in contrast to the influence on zwitterionic phospholipids. In phosphatidic acid this is expressed in the formation of an HII phase; in phosphatidylglycerol a less ordered, non-lamellar structure with low water content is adopted.

Bee Venoms↗
PubMed1985

Freeze-fracture studies of human blood platelets activated by thrombin using rapid freezing.

In this study the influence of thrombin activation on human blood platelets has been followed by freeze-fracturing electron microscopy using rapid freezing in order to catch the initial changes in shape and the morphological alterations during the process of exocytosis of secretory granules. We found that isolation of the platelets by itself leads to some degree of shape change, which made it impossible to study the resting discoid platelet by rapid freezing. Activation of the platelets by thrombin induced dilation of the "surface connecting system (SCS)" with formation of large vacuoles as a result of fusion of the secretory granules with SCS. No intermediary fusion stages or structures were observed even using rapid freezing. Volcano-like protrusions and the corresponding complementary pits were seen at the SCS. These structures were interpreted by us as fractures through protoplasmic channels crossing the SCS. These channels originate during the swelling of the SCS as a result of the fusion of secretory granules with the SCS.

Blood Platelets↗
PubMed1985

Ultrastructural changes of sarcolemma and mitochondria in the isolated rabbit heart during ischemia and reperfusion.

Isolated rabbit hearts were perfused by the Langendorff technique, made ischemic and subsequently reperfused. It was found that ischemia results in: (i) aggregation of the intramembranous particles in the sarcolemma and (ii) extrusion of pure lipidic multilamellar structures (liposomes) from swollen mitochondria. Subsequent reperfusion resulted in further aggregation of the sarcolemmal intramembranous particles and disruption of the sarcolemma, which was attended by the formation of liposome-like structures. Intramembrane particle aggregation is explained in terms of lateral phase separation of the membrane lipids and a reduction of repulsive forces between the membrane proteins, both induced by a decrease in pH and an increase in Ca2+ concentration intracellularly. The formation and extrusion of the multilamellar structures are discussed in terms of destabilization of the bilayer which results in a structural blebbing-off of pure lipid.

Animals↗
PubMed1985

Sarcolemmal disruption during the calcium paradox.

Reperfusion of an isolated heart with calcium-containing solution after a short period of calcium-free perfusion may result in irreversible cell damage (calcium paradox). The ultrastructure of the sarcolemma of the rabbit heart during the calcium paradox was studied by using fast freezing devices. This method excluded ultrastructural changes induced by chemical fixation and cryoprotection. In addition, thin-section and conventional freeze-fracture electron microscopy were used. During reperfusion with calcium-containing solution disruption of the sarcolemma was observed, which was attended with formation of unilamellar and multilamellar vesicles and aggregation of intramembrane particles. These ultrastructural changes are explained in terms of calcium- and proton-induced lateral phase separation and fusion processes in the lipid bilayer of the sarcolemma.

Animals↗
PubMed1984

Non-bilayer structures in membrane fusion.

Membrane fusion is an ubiquitous event in cell biology. One can distinguish two types of fusion: (i) outside/outside fusion, for example endocytosis, and (ii) inside/inside fusion, for example exocytosis. In spite of this difference in types of fusion in relation to membrane asymmetry and in spite of the large variety of lipid compositions encountered in biological membranes, a universal mechanism can be postulated for the role of lipids in membrane fusion. In this concept the lipids leave the bilayer configuration temporarily and locally. This notion, and the fact that any biological membrane contains a substantial amount of lipids which prefer the non-bilayer hexagonal II phase in physiological conditions, has led to the hypothesis that such hexagonal II phase lipids play a crucial role in membrane fusion. This proposition is strongly supported by model membrane experiments in which it has been demonstrated that factors such as Ca2+ and temperature, which trigger the transition from bilayer to hexagonal II phase, in fact induce membrane fusion.

Animals↗
PubMed1982

Further aspects of the Ca2+-dependent polymorphism of bovine heart cardiolipin.

The influence of cations on the structure of aqueous dispersions of the sodium salt of bovine heart cardiolipin was investigated using binding experiments, 31P-NMR, freeze-fracture electron microscopy, small angle X-ray diffraction and batch calorimetry techniques. In the 1-3 mM concentration range, Ca2 induces a bilayer leads to hexagonal HII transition for the lipid. During this transition there is a marked increase in Ca2+ binding from a maximum of 0.35 Ca/cardiolipin in the bilayer to 1.0 Ca/cardiolipin in the hexagonal HII phase. Only when the cardiolipin liposomes are exposed to locally high Ca2+ concentrations is the bilayer leads to hexagonal HII transition accompanied by the appearance of an intermediate 'isotropic' structure characterized by an isotropic 31P-NMR signal and lipidic particles. In contrast, in mixed dioleoylphosphatidylcholine/cardiolipin (1:1) liposomes, Ca2+ concentrations as low as 100 microM will induce an 'isotropic' structure under conditions where no locally high Ca2+ concentrations can occur. In this system at higher Ca2+ concentrations (above 5 mM) the hexagonal HII phase formation occurs. At least 80% of the phosphatidylcholine can be incorporated into this phase. The Ca2+ -induced bilayer to hexagonal transition is an endothermic reaction with a delta H of approx. 1.8 kcal/mol. Removal of Ca2+ from the hexagonally organized calcium-cardiolipin (1:1) complex by dialysis is an extremely slow process with a half-time in excess of 80 h. After 23 h of dialysis at a Ca/cardiolipin ratio of 0.86 an 'isotropic' structure is observed, characterized by an isotropic 31P-NMR signal and the presence of lipidic particles. After 70 h of dialysis (Ca/cardiolipin = 0.7) a new phase is observed. This phase which is optically isotropic and highly viscous separates from a lipid-free aqueous phase and contains 111 mM cardiolipin (15.5% by weight). The phospholipid molecules undergo rapid isotropic motion and the freeze-fracture morphology indicates the presence of a highly curved interconnected bilayer network separating various aqueous compartments. No defined X-ray diffraction bands can be observed for this phase. These characteristics are typical for cubic phases. This phase is metastable as mechanical agitation immediately induces the formation of large bilayer vesicles.

Animals↗
PubMed1982

Divalent cations and chlorpromazine can induce non-bilayer structures in phosphatidic acid-containing model membranes.

(1) The structural organization of aqueous dispersions of 1,2-dioleoylphosphatidic acid has been investigated by freeze-fracture electron microscopy in relation to variations in pH, divalent cations and the local anaesthetic chlorpromazine. (2) In the pH range 4--8 in the presence of 100 mM Na+, dioleoylphosphatidic acid is organized in bilayers. (3) At pH 6 and not at pH 4 and 8.5 addition of Ca2+, Mg2+, Mn2+ and chlorpromazine results in the formation of the hexagonal HII phase. (4) Ca2+ and chlorpromazine addition to mixed phosphatidylcholine-dioleoylphosphatidic acid bilayers at pH 6 results in the formation of lipidic particles.

Calcium↗
PubMed1981

Ca2+-induced changes in the barrier properties of cardiolipin/phosphatidylcholine bilayers.

(1) A selective increase in permeability is induced in cardiolipin/phosphatidylcholine bilayers at Ca2+ concentrations of 1--3 mM. At higher concentrations of Ca2+ the permeability barrier is completely destroyed. (2) The selective increase in permeability is correlated with the formation of lipid particles visualized by freeze-fracture electron microscopy and an isotropic signal in 31P-NMR spectra. (3) Lowering the Ca2+ concentration shows reduction in permeability but the formation of the lipid particles is a non-reversible process. (4) At higher Ca2+ concentrations, 31P-NMR spectra and freeze-fracture results indicate the formation of the hexagonal phase, explaining the disappearance of the permeability barrier.

Calcium↗
PubMed1981

31P-Nuclear magnetic resonance and freeze-fracture electron microscopic studies on reconstituted bacteriorhodopsin vesicles.

Bacteriorhodopsin has been reconstituted into egg-phosphatidylcholine vesicles by various methods. The resulting preparations have been analyzed on density gradients and by freeze-fracture electron microscopy. The homogeneity of the vesicle preparations and the light-induced intravesicular pH changes have been studied by 31P-NMR, using glucose 6-phosphate as pH probe. It is concluded that bacteriorhodopsin is incorporated in the inside-out mode in vesicles up to about 100 nm. Above this diameter, more or less random insertion takes place.

Bacteriorhodopsins↗
PubMed1981

Lipidic particles.

A new type of lipid organization is observed in mixtures of phosphatidylcholine with cardiolipin in the presence of Ca++, monoglucosyldiglyceride and phosphatidylethanolamine (in the presence of cholesterol). This phase is characterized by an isotropic 31P NMR signal and is visualized by freeze fracturing as particles and pits on the fracture faces of the lipid bilayer. As the most favourable model for this phase we propose the inverted micelle sandwiched in between the two monolayers of the lipid bilayer. It will be shown that such particles and pits appear on the fusion site during fusion of unilamellar vesicles of an equimolar mixture of phosphatidylcholine and cardiolipin in the presence of Ca++.

Calcium↗
PubMed1980

Phosphatidylcholesterol bilayers. A model for phospholipid-cholesterol interaction.

Aqueous dispersions of monovalent and divalent cations salts of O-(1,2-dipalmitosyl-sn-glycero-3-phosphoryl)cholesterol form multilamellar vesicles as shown by freeze-fracture electron microscopy, by electron micrographs of the negatively stained liposomes, and by swelling curves of liposomes in hypo-osmotic medium. Differential scanning calorimetry reveals that aqueous dispersions of divalent metal salts of O-(1,2-dipalmitoyl-sn-glycero-3-phosphoryl)cholesterol undergo a characteristic thermotropic phase transition with a relatively large cooperative unit (n greater than 250 for the calcium salt). In contrast, monovalent cation salts of O-(1,2-dipalmitoyl-sn-glycero-3-phosphoryl)cholesterol do not show a thermotropic phase transition under comparable conditions. The molecular area of 0-(1,2-dipalmitoyl-sn-glycero-3-phosphoryl)cholesterol in a monolayer is the same in the presence and absence of Ca2+, and is virtually equal to the area of an equimolar mixture of dipalmitoyl phosphatidic acid and cholesterol. To account for the novel state induced by Ca2+, on aqueous dispersions of O-(1,2-dipalmitoyl-sn-glycero-3-phosphoryl)cholesterol (i.e., bilayer organization and highly cooperative phase transition), a linear array model is proposed in which Ca2+ bridges adjacent arrays of O-(1,2-dipalmitoyl-sn-glycero-3-phosphoryl)cholesterol molecules, thus freezing the acyl chains in their normal state. One of the main corollaries of the model is that the cooperative unit for a thermotropic phase transition is essentially one-dimensional, rather than a two-dimensional matrix. O-(1,2-Dipalmitoyl-sn-glycero-3-phosphoryl)cholesterol is proposed as an orientationally and conformationally restricted analog of glycerophospholipid plus cholesterol in bilayers.

Cholesterol↗
PubMed1978

Architecture of the outer membrane of Escherichia coli. III. Protein-lipopolysaccharide complexes in intramembraneous particles.

In a previous paper (A. Verkleij, L. van Alphen, J. Bijvelt, and B. Lugtenberg, Biochim. Biophys. Acta 466:269-282, 1977) we have hypothesized that particles on the outer fracture face of the outer membrane ([Formula: see text]), with corresponding pits on the inner fracture face of the outer membrane ([Formula: see text]), consist of lipopolysaccharide (LPS) aggregates stabilized by divalent cations and that they might contain protein and/or phospholipid. In the present paper the roles of LPS, cations, and proteins in these [Formula: see text] particles are described more extensively, using a strain that lacks the major outer membrane proteins, b, c, and d (b(-) c(-) d(-)), and has a reduction in the number of [Formula: see text] particles of 75%. To study the role of divalent cations in the formation of [Formula: see text] particles, these b(-) c(-) d(-) cells were grown or incubated with Ca(2+), Mg(2+), or putrescine. The presence of Ca(2+) resulted in the appearance of many [Formula: see text] particles and [Formula: see text] pits. Mg(2+) and putrescine were less effective than Ca(2+). Introduction of these particles was not accompanied by alterations in the relative amounts of LPS and cell envelope proteins. Ca(2+) treatment of a heptoseless derivative of a b(-) c(-) d(-) strain did not result in morphological changes. Incubation of Ca(2+)-treated cells with ethylenediaminetetraacetate caused the disappearance of the introduced particles as well as the release of more than 60% of the cellular LPS. These results strongly support the hypothesis that LPS is involved in the formation of [Formula: see text] particles and [Formula: see text] pits. The roles of various outer membrane proteins in the formation of [Formula: see text] particles were studied by comparing the freeze-fracture morphology of b(-) c(-) d(-) cells with that of cells which contain one of the outer membrane proteins b, c, d, and e or the receptor protein for bacteriophage lambda. The results showed that the presence of any of these five proteins in a b(-) c(-) d(-) background resulted in a large increase in the number of [Formula: see text] particles and [Formula: see text] pits, indicating that these proteins are, independent of each other, involved in the formation of [Formula: see text] particles and [Formula: see text] pits. The simplest explanation for the results is that in wild-type cells each particle consists of LPS complexed with some molecules of a single protein species, stabilized by either divalent cations or polyamines. It is hypothesized that the outer membrane of the wild-type cell contains a heterogeneous population of particles, of which 75% consists of protein b-LPS, protein c-LPS, and protein d-LPS particles. A function of these particles as aqueous pores is proposed.

Bacterial Proteins↗
PubMedDate not supplied

Phospholipase A2 activity in platelets. Immuno-purification and localization of the enzyme in rat platelets.

A comparative study on phospholipase A2 activity in platelet lysates from various species was carried out using identical assay conditions with phosphatidylethanolamine as substrate. Platelet phospholipase A2, both when expressed as activity per ml blood and as specific activity in KCl extracts, was low in human, cow, pig and goat. Moderate activities, in increasing order, were found in sheep, horse and rabbit, while rats showed by far the highest activity. In the latter four species total lysate activity was recovered in 1 M KCl extracts, suggesting that the enzyme occurs either in soluble form or as a peripheral membrane-associated protein. Immune cross-reactivity with monoclonal antibodies against rat liver mitochondrial phospholipase A2 was studied in dot-blot and monoclonal antibody-Sepharose binding experiments. Only sheep and rat platelet extracts contained cross-reactive phospholipase(s) A2. Immuno-affinity chromatography of rat platelet extracts indicated virtually complete binding of total phospholipase A2 activity and yielded pure enzyme in a single purification step. Enzyme visualization by immunogold electron microscopy showed a predominant localization in the matrix of alpha-granules.

Animals↗