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Membrane Deterioration in Senescing Carnation Flowers 1: Coordinated Effects of Phospholipid Degradation and the Action of Membranous Lipoxygenase

Fobel, Maribeth; Lynch, Daniel V.; Thompson, John E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1987 EN
Relevância na Pesquisa
57.68786%
The lipid fluidity of microsomal membranes from the petals of cut carnation flowers decreases as the flowers senesce. A comparable change in fluidity was induced by in vitro aging of microsomal membranes from young flowers under conditions in which membranous lipoxygenase-like activity was active. There was no change in fluidity when the membranes were aged in the presence of inhibitors of lipoxygenase or were heat-denatured prior to aging. Membranes from naturally senesced flowers and membranes that had been aged in vitro both sustained an increase in saturated:unsaturated fatty acid ratio that accounted for the decrease in lipid fluidity, and in both instances there was evidence for depletion of the unsaturated fatty acids, linoleic acid, and linolenic acid, which are substrates for lipoxygenase. Loss of lipid phosphate reflecting breakdown of membrane phospholipids preceded the depletion of unsaturated fatty acids attributable to the lipoxygenase-like activity. The data have been interpreted as indicating that fatty acid substrates for membrane-associated lipoxygenase-like activity are made available by the initiation of phospholipid degradation, and that the utilization of these substrates results in a selective depletion of unsaturated fatty acids from the membrane and an ensuing decrease in bulk lipid fluidity.

Molecular Species Specificity of Phospholipid Breakdown in Microsomal Membranes of Senescing Carnation Flowers 1

Brown, J. H.; Lynch, D. V.; Thompson, John E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1987 EN
Relevância na Pesquisa
57.680024%
During senescence of cut carnation flowers, there is extensive breakdown of microsomal phospholipid. This is attributable, at least in part, to lipolytic activity associated directly with the microsomal membranes. Evidence indicating that one or more of the lipid-degrading enzymes in these membranes preferentially degrade phospholipid molecular species containing two diunsaturated acyl chains or at least one polyunsaturated acyl chain has been obtained by using radiolabeled phosphatidylcholine substrates. 16:0*/16:0*, 16:0/18:2*, and 18:1*/18:1* phosphatidylcholine were degraded only minimally over a 3 hour period by microsomes isolated from senescing flowers. By contrast, [U-14C]phosphatidylcholine, which comprises various molecular species including those containing polyunsaturated acyl chains, and 18:0/20:4* phosphatidylcholine were extensively degraded. Under identical conditions, but in the absence of added radiolabeled substrate, endogenous 18:2/18:2, 18:1/18:3, and 18:2/18:3 phosphatidylcholine were selectively depleted from the membranes. During natural senescence of the flowers, there was a sharp decline in microsomal 16:0/18:1 and 18:1/18:2 phosphatidylcholine, whereas molecular species containing two diunsaturated acyl chains or at least one polyunsaturated acyl chain remained unchanged or decreased only slightly. The data have been interpreted as indicating that provision of particular molecular species susceptible to lipase attack is a prerequisite to phospholipid catabolism in senescing membranes.

Preparation and Characterization of Envelope Membranes from Nongreen Plastids

Alban, Claude; Joyard, Jacques; Douce, Roland
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1988 EN
Relevância na Pesquisa
57.778574%
We have developed a reliable procedure for the purification of envelope membranes from cauliflower (Brassica oleracea L.) bud plastids and sycamore (Acer pseudoplatanus L.) cell amyloplasts. After disruption of purified intact plastids, separation of envelope membranes was achieved by centrifugation on a linear sucrose gradient. A membrane fraction, having a density of 1.122 grams per cubic centimeter and containing carotenoids, was identified as the plastid envelope by the presence of monogalactosyldiacylglycerol synthase. Using antibodies raised against spinach chloroplast envelope polypeptides E24 and E30, we have demonstrated that both the outer and the inner envelope membranes were present in this envelope fraction. The major polypeptide in the envelope fractions from sycamore and cauliflower plastids was identified immunologically as the phosphate translocator. In the envelope membranes from cauliflower and sycamore plastids, the major glycerolipids were monogalactosyldiacylglycerol, digalactosyldiacylglycerol, and phosphatidylcholine. Purified envelope membranes from cauliflower bud plastids and sycamore amyloplasts also contained a galactolipid:galactolipid galactosyltransferase, enzymes for phosphatidic acid and diacylglycerol biosynthesis...

A Comparative Spin-Label Study of Isolated Plasma Membranes and Plasma Membranes of Whole Cells and Protoplasts from Cold-Hardened and Nonhardened Winter Rye

Windle, John J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/1988 EN
Relevância na Pesquisa
77.70058%
Lipid-lipid and lipid-protein interactions in the plasma membranes of whole cells and protoplasts and an isolated plasma membrane fraction from winter rye (Secale cereale L. cv Puma) have been studied by spin labeling. Spectra were recorded between −40°C and 40°C using the freely diffusing spin-label, 16-doxyl stearic acid, as a midbilayer membrane probe. The probe was reduced by the whole cells and protoplasts and reoxidized by external potassium ferricyanide. The reoxidized probe was assumed to be localized in the plasma membrane. The spectra consisted of the superposition of a narrow and a broad component indicating that both fluid and immobilized lipids were present in the plasma membrane. The two components were separated by digital subtraction of the immobilized component. Temperature profiles of the membranes were developed using the percentage of immobilized lipid present at each temperature and the separation between the outermost hyperfine lines for the fluid lipid component. Lipid immobilization was attributed to lipid-protein interactions, lipid-cell wall interactions, and temperature-induced lipid phase transitions to the gel-state. Temperature profiles were compared for both cold-hardened and nonhardened protoplasts...

In Vitro Synthesis, Assembly and Function of a Photosynthetic Membrane Protein 1

Michaels, Allan; Herrin, David
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1989 EN
Relevância na Pesquisa
57.710137%
Cell-free translation of Chlamydomonas reinhardtii RNA in the presence of photosynthetic membranes resulted in association of the herbicide binding (Qb) protein with membranes. Incubation of recovered membranes with high salt did not extract the polypeptide from membranes. Tryptic digestion of in vivo labeled membranes or membranes recovered from in vitro translation mixtures showed that Qb had similar orientation. In vitro translation in the presence of chloroplast membranes from cells exposed to high light intensity restored the membrane associated kinase activity lost by photoinhibition. Thus, in vitro synthesis resulted in functional integration of the Qb protein within the photosynthetic membrane.

Protein Kinase Activities in Tonoplast and Plasmalemma Membranes from Corn Roots

Ladror, Uri S.; Zielinski, Raymond E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1989 EN
Relevância na Pesquisa
57.590483%
Protein kinase and phosphatase activities were studied in plasmalemma and tonoplast membrane fractions from corn (Zea mays L.) roots in order to test the hypothesis that the tonoplast H+-ATPase is regulated by intrinsic protein phosphorylation (G Zocchi, SA Rogers, JB Hanson 1983 Plant Sci Lett 31: 215-221), and to facilitate future purification of kinase activities from these membranes. Kinase activity in the plasmalemma was about three-fold higher than in the tonoplast, and displayed Michaelis Menten-type behavior with a Km value for MgATP2− of about 50 micromolar. Both activities were optimal at 3 millimolar free Mg2+ and had pH optima at 6.6 and 7.0 for the plasmalemma and tonoplast, respectively. Kinase activities in both fractions were stimulated by 1 micromolar free Ca2+, but calmodulin had no stimulatory effect, and chlorpromazine was inhibitory only at high concentrations. The pattern of phosphopeptides on SDS polyacrylamide gel electrophoresis was similar in both fractions except for one band of 50 kilodaltons that was present only in the tonoplast. A partially purified H+-ATPase fraction was prepared from tonoplast membranes, incubated under conditions optimal for protein phosphorylation. The three polypeptides (of 67...

Photosynthetic Apparatus of Pea Thylakoid Membranes 1: Response to Growth Light Intensity

Lee, Wen-Jane; Whitmarsh, John
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1989 EN
Relevância na Pesquisa
57.68786%
We investigated the effect of growth light intensity on the photosynthetic apparatus of pea (Pisum sativum) thylakoid membranes. Plants were grown either in a growth chamber at light intensities that ranged from 8 to 1050 microeinsteins per square meter per second, or outside under natural sunlight. In thylakoid membranes we determined: the amounts of active and inactive photosystem II, photosystem I, cytochrome b/f, and high potential cytochrome b559, the rate of uncoupled electron transport, and the ratio of chlorophyll a to b. In leaves we determined: the amounts of the photosynthetic components per leaf area, the fresh weight per leaf area, the rate of electron transport, and the light compensation point. To minimize factors other than growth light intensity that may alter the photosynthetic apparatus, we focused on peas grown above the light compensation point (20-40 microeinsteins per square meter per second), and harvested only the unshaded leaves at the top of the plant. The maximum difference in the concentrations of the photosynthetic components was about 30% in thylakoids isolated from plants grown over a 10-fold range in light intensity, 100 to 1050 microeinsteins per square meter per second. Plants grown under natural sunlight were virtually indistinguishable from plants grown in growth chambers at the higher light intensities. On a leaf area basis...

Immunochemical Analysis Shows That an ATP/ADP-Translocator Is Associated with the Inner-Envelope Membranes of Amyloplasts from Acer pseudoplatanus L. 1

Ngernprasirtsiri, Jarunya; Takabe, Tetsuko; Akazawa, Takashi
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1989 EN
Relevância na Pesquisa
57.68786%
Pure preparations of intact amyloplasts and chloroplasts, free from mitochondrial contamination, were isolated from cultured cells of the white-wild and green-mutant lines of sycamore (Acer pseudoplatanus L.), respectively. A specific rabbit antiserum against yeast mitochondrial cytochrome c1 only cross-reacted with mitochondrial membranes from the white-wild sycamore cells. The outer and inner envelope-membranes of the two plastid-types were isolated and subsequently analyzed by sodium dodecylsulfate-polyacrylamide gel electrophoresis to characterize polypeptide patterns in each fraction. Analysis by immunoblotting clearly showed that antiserum against the 29-kilodalton inorganic orthophosphate translocator isolated from pea chloroplasts cross-reacted with a 31-kilodalton polypeptide residing in the inner-envelope membranes from both sycamore chloroplasts and amyloplasts. In contrast, antiserum against the ADP/ATP-translocator isolated from mitochondria of Neurospora crassa yielded a positive signal with a 32-kilodalton polypeptide in the inner-membranes isolated from amyloplasts, but not green-mutant chloroplasts. We propose that this 32-kilodalton polypeptide in the amyloplast envelope is a putative ATP/ADP-translocator and its possible functional significance is discussed.

Studies on 17,24 kD Depleted Photosystem II Membranes 1: I. Evidences for High and Low Affinity Calcium Sites in 17,24 kD Depleted PSII Membranes from Wheat versus Spinach

Cammarata, Kirk V.; Cheniae, George M.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1987 EN
Relevância na Pesquisa
57.69583%
Analyses were made of the effects of extraction of the 17,24 kilodalton extrinsic proteins from spinach versus wheat photosystem II (PSII) membranes on Ca abundance and O2 evolution capacity determined in the absence and presence of either Cl− or Ca2+. Extraction of these proteins from spinach PSII routinely diminished steady state O2 evolution by about 70% when assayed in the presence of sufficient Cl−. Additionally, O2 evolution of 17,24 kilodalton-less spinach PSII membranes showed about 2-fold more enhancement by Ca2+ than by Cl− during assay. When the same extraction and assay procedures were applied to wheat PSII membranes, we observed, in contrast to 17,24 kilodalton-less spinach PSII, only about 50% inhibition of O2 evolution and about 2-fold greater enhancement by Cl− than by Ca2+. Irrespective of differences in the magnitude of enhancement of O2 evolution by Ca2+versus Cl− in spinach versus wheat, the Km values for Cl− (about 1.7 millimolar) and Ca2+ (about 1.5 millimolar) were similar for both type preparations. The abundance of Ca specifically associated with fully functional PSII (about 2 and about 3 Ca/200 chlorophyll for spinach and wheat, respectively) was diminished to about 1 per 200 chlorophyll upon 17.24 kilodalton protein depletion. Further treatment of wheat 17...

Effect of Ca2+ and Calmodulin on ΔpH Formation in Tonoplast Vesicles from Corn Roots 1

Ladror, Uri S.; Zielinski, Raymond E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1990 EN
Relevância na Pesquisa
67.33362%
The effects of calmodulin (CaM) on ATPase activity and ATP-dependent formation of a proton gradient (ΔpH) were studied in tonoplast membrane vesicles from corn (Zea mays L.) roots. At 0.6 micromolar, CaM stimulated ATPase activity by about 20% in the absence of an uncoupler, but by only 4% in its presence. Thus, the uncoupler-dependent increment of activity was decreased 30 to 45% by CaM. The formation of a proton gradient across the membrane vesicle, measured by quinacrine fluorescence quench, was inhibited about 20% by CaM. Its effect was additive to the effect of Ca2+ and was completely abolished by EGTA. These effects of CaM could be due to stimulation of H+ efflux or due to inhibition of the H+-ATPase. To distinguish between these possibilities, we examined the effect of CaM on dissipation of preformed ΔpH after the ATPase was inhibited. CaM stimulated the dissipation of a preformed ΔpH by 40% after the H+-ATPase was inhibited with NO3−. This indicates that CaM facilitates the recycling of protons across the tonoplast membranes and does not regulate the H+-ATPase by direct inhibition.

Boron Induces Hyperpolarization of Sunflower Root Cell Membranes and Increases Membrane Permeability to K+1

Schon, Mary K.; Novacky, Anton; Blevins, Dale G.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1990 EN
Relevância na Pesquisa
67.573438%
Although many studies have alluded to a role for boron (B) in membrane function, there is little evidence for a direct effect of B on the plasmalemma of higher plant cells. These studies were conducted to demonstrate, by electrophysiological techniques, a direct effect of B on the membrane potential (Em) of sunflower (Helianthus annuus [L.], cv Mammoth Grey Stripe) root tip cells and to determine if the response to B occurs rapidly enough to account for the previously observed effects of B on ion uptake. By inserting a glass microelectrode into an individual cell in the root tip, the Em of the cell was determined in basal salt medium (BSM), pH 6.0. The perfusion solution surrounding the root tissue was then changed to BSM + 50 micromolar H3BO3, pH 6.0. The exposure to B induced a significant plasmalemma hyperpolarization in sunflower root cells within 20 minutes. After just 3 minutes of exposure to B, the change in Em was already significantly different from the negligible change in Em observed over time in root cells never exposed to B. Membrane hyperpolarization could be caused by a stimulation of the proton pump or by a change in the conductance of one or more permeable ions. Since B has been shown to affect K+ uptake by plants...

Calcium Transport in the Green Alga Mesotaenium caldariorum1: Preliminary Characterization and Subcellular Distribution

Berkelman, Tom; Lagarias, J. Clark
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1990 EN
Relevância na Pesquisa
67.489917%
The subcellular localization and biochemical characterization of calcium transport were studied in the unicellular green alga Mesotaenium caldariorum. Membrane fractions prepared by osmotic lysis of Mesotaenium protoplasts exhibit high rates of ATP-dependent calcium uptake. Sucrose gradient centrifugation separates two pools of activity, which display specific activities for calcium transport as high as 15 nanomoles Ca2+ per minute per milligram of protein. Marker enzyme analysis shows that this dual distribution of calcium transport activity is similar to that of vanadate-insensitive ATPase and pyrophosphatase, activities considered to be associated with the tonoplast. Plasma membranes, endoplasmic reticulum vesicles, mitochondrial membranes, and thylakoids band at higher densities than either calcium transport fraction. Both pools of ATP-dependent calcium uptake contain two components which are not separable on sucrose gradients but can be distinguished on the basis of inhibitor sensitivity. One component is inhibited by nigericin or trimethyltin chloride (I50 values of 3 nanomolar and 4 micromolar, respectively), while the other component is vanadate sensitive (I50 of 25 micromolar). These results suggest that direct Ca2+ transport and Ca2+/H+ antiport activities are present in both sucrose gradient fractions.

Ascorbate Free-Radical Reduction by Glyoxysomal Membranes 1

Bowditch, Mark l.; Donaldson, Robert P.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1990 EN
Relevância na Pesquisa
57.645806%
Glyoxysomal membranes from germinating castor bean (Ricinus communis L. cv Hale) endosperm contain an NADH dehydrogenase. This enzyme can utilize extraorganellar ascorbate free-radical as a substrate and can oxidize NADH at a rate which can support intraglyoxysomal demand for NAD+. NADH:ascorbate free-radical reductase was found to be membrane-associated, and the activity remained in the membrane fraction after lysis of glyoxysomes by osmotic shock, followed by pelleting of the membranes. In whole glyoxysomes, NADH:ascorbate free-radical reductase, like NADH:ferricyanide reductase and unlike NADH:cytochrome c reductase, was insensitive to trypsin and was not inactivated by Triton X-100 detergent. These results suggest that ascorbate free-radical is reduced by the same component which reduces ferricyanide in the glyoxysomal membrane redox system. NADH:ascorbate free-radical reductase comigrated with NADH:ferricyanide and cytochrome c reductases when glyoxy-somal membranes were solubilized with detergent and subjected to rate-zonal centrifugation. The results suggest that ascorbate free-radical, when reduced to ascorbate by membrane redox system, could serve as a link between glyoxysomal metabolism and other cellular activities.

NADH-Ferricyanide Reductase of Leaf Plasma Membranes 1: Partial Purification and Immunological Relation to Potato Tuber Microsomal NADH-Ferricyanide Reductase and Spinach Leaf NADH-Nitrate Reductase

Askerlund, Per; Laurent, Pascal; Nakagawa, Hiroki; Kader, Jean-Claude
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1991 EN
Relevância na Pesquisa
57.690503%
Plasma membranes obtained by two-phase partitioning of microsomal fractions from spinach (Spinacea oleracea L. cv Medania) and sugar beet leaves (Beta vulgaris L.) contained relatively high NADH-ferricyanide reductase and NADH-nitrate reductase (NR; EC 1.6.6.1) activities. Both of these activities were latent. To investigate whether these activities were due to the same enzyme, plasma membrane polypeptides were separated with SDS-PAGE and analyzed with immunoblotting methods. Antibodies raised against microsomal NADH-ferricyanide reductase (tentatively identified as NADH-cytochrome b5 reductase, EC 1.6.2.2), purified from potato (Solanum tuberosum L. cv Bintje) tuber microsomes, displayed one single band at 43 kilodaltons when reacted with spinach plasma membranes, whereas lgG produced against NR from spinach leaves gave a major band at 110 kilodaltons together with a few fainter bands of lower molecular mass. Immunoblotting analysis using inside-out and right-side-out plasma membrane vesicles strongly indicated that NR was not an integral protein but probably trapped inside the plasma membrane vesicles during homogenization. Proteins from spinach plasma membranes were solubilized with the zwitterionic detergent 3-[(3-cholamidopropyl) dimethylammonio] 1-propane-sulfonate and separated on a Mono Q anion exchange column at pH 5.6 with fast protein liquid chromatography. One major peak of NADH-ferricyanide reductase activity was found after separation. The peak fraction was enriched about 70-fold in this activity compared to the plasma membrane. When the peak fractions were analyzed with SDS-PAGE the NADH-ferricyanide reductase activity strongly correlated with a 43 kilodalton polypeptide which reacted with the antibodies against potato microsomal NADH-ferricyanide reductase. Thus...

Diurnal Fluctuations in the Content and Functional Properties of the Light Harvesting Chlorophyll a/b Complex in Thylakoid Membranes 1: Correlation with the Diurnal Rhythm of the mRNA Level

Busheva, Mira; Garab, Gyözö; Liker, Erika; Tóth, Zsuzsanna; Szèll, Màrta; Nagy, Ferenc
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1991 EN
Relevância na Pesquisa
57.63979%
Diurnal fluctuations were observed in the content and some structural and functional properties of the light-harvesting chlorophyll (Chl) a/b pigment-protein complex of photosystem II (LHCII) in young developing wheat (Triticum aestivum) leaves grown under 16 hours light/8 hours dark illumination regime. The fluctuations could be correlated with the diurnal oscillation in the level of mRNA for LHCII. The most pronounced changes occurred in the basal segments of the leaves. They were weaker or hardly discernible in the middle and tip segments. As judged from the diurnal variations of the Chl-a/Chl-b molar ratio, the LHCII content of the thylakoid membranes peaked around 2 pm. This can be accounted for by the cumulative effect of the elevated level of mRNA in the morning and early afternoon. In the basal segment, the extent of the fluctuation in the LHCII content was approximately 25%, as determined from gel electrophoresis (“green gels”). The amplitude of the principal bands of the circular dichroism (CD) spectra of isolated chloroplasts paralleled the changes in the LHCII content. Our circular dichroism data suggest that the newly synthesized LHCII complexes are incorporated into the existing helically organized macrodomains of the pigment-protein complexes or themselves form such macrodomains in the thylakoid membranes. Chl-a fluorescence induction kinetics also showed diurnal variations especially in the basal segments of the leaves. This most likely indicates fluctuations in the ability of membranes to undergo “state transitions.” These observations suggest a physiological role of diurnal rhythm of mRNA for LHCII in young developing leaves.

Assembly of Two Subunits of the Cyanobacterial Photosystem I on the n-Side of Thylakoid Membranes

Chitnis, Parag R.; Nelson, Nathan
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/1992 EN
Relevância na Pesquisa
67.774136%
Photosystem I contains several peripheral membrane proteins that are located on either positive (luminal) or negative (stromal or cytoplasmic) sides of thylakoid membranes of chloroplasts or cyanobacteria. Incorporation of two peripheral subunits into photosystem I of the cyanobacterium Synechocystis species PCC 6803 was studied using a reconstitution system in which radiolabeled subunits II (PsaD) and IV (PsaE) were synthesized in vitro and incubated with the isolated thylakoid membranes. After such incubation, the subunits were found in the membranes and were resistant to digestion with proteases and removal by 2 molar NaBr. All of the radioactive proteins incorporated in the membrane were found in the photosystem I complex. The subunit II was assembled specifically into cyanobacterial thylakoid membranes and not into Escherichia coli cell membranes or thylakoid membranes isolated from spinach. The assembly process did not require ATP or proton motive force, and it was not stimulated by ATP. The assembly of subunits II and IV into thylakoid membranes isolated from the strain AEK2, which lacks the gene psaE, was increased two- to threefold. The incorporation of subunit II was 15 to 17 times higher in the thylakoids obtained from the strain ADK3 in which the gene psaD has been inactivated. However...

Identification and Characterization of the ictA/ndhL Gene Product Essential to Inorganic Carbon Transport of Synechocystis PCC6803 1

Ogawa, Teruo
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1992 EN
Relevância na Pesquisa
57.652373%
The ictA gene, renamed ndhL in this paper, essential to inorganic carbon transport of Synechocystis PCC6803, was expressed in Eschericia coli as a fusion protein with glutathione S-transferase. An antibody was raised against this fusion protein. Western analysis of the thylakoid membrane of wild-type (WT) Synechocystis revealed that a protein with an apparent molecular mass of 6.7 kilodaltons cross-reacted with this antibody. No immunoreactive protein was present in the thylakoid membranes of the Synechocystis mutants, RKb and M9, which have defects in the ictA/ndhL gene, or in the cytoplasmic membranes of the WT and mutant cells. Thus, the protein reacted with the antibody is the ictA gene product (IctA) and is localized in the thylakoid membrane of WT cells. IctA was absent in the thylakoid membranes of the M55 mutant, in which the ndhB gene is inactivated, and was poorly immunostained in the membranes of the mutants (M-ndhC and M-ndhK) constructed by inactivating the ndhC and ndhK genes of WT Synechocystis, respectively. The carbon dioxide uptake activity was nearly zero in M-ndhK and was about 40% of the activity of WT cells in M-ndhC. The RKb, M-ndhC, and M-ndhK mutants were unable to grow or grew very slowly under photoheterotrophic conditions. These results indicated that NADH dehydrogenase is essential to inorganic carbon transport and photoheterotrophic growth of Synechocystis and that IctA is one of the subunits of this enzyme.

Origin of Thylakoid Membranes in Chlamydomonas reinhardtii y-1 at 38°C 1

Hoober, J. Kenneth; Boyd, Charles O.; Paavola, Laurie G.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1991 EN
Relevância na Pesquisa
57.62002%
The origin of thylakoid membranes was studied in Chlamydomonas reinhardtii y-1 cells during greening at 38°C. Previous studies showed that, when dark-grown cells are exposed to light under these conditions, the initial rates of accumulation of chlorophyll and the chlorophyll a/b-binding proteins in membranes are maximal (MA Maloney JK Hoober, DB Marks [1989] Plant Physiol 91: 1100-1106; JK Hoober MA Maloney, LR Asbury, DB Marks [1990] Plant Physiol 92: 419-426). As shown in this paper, photosystem II activity, which was nearly absent in dark-grown cells, also increased at a linear rate in parallel with chlorophyll. As compared with those made at 25°C, photosystem II units assembled during greening at 38°C were photochemically more efficient, as judged by saturation at a lower fluence of light and a negligible loss of excitation energy as fluorescence. Electron microscopy of cells in light for 5 or 15 minutes at 38°C showed that these initial, functional thylakoid membranes developed in association with the chloroplast envelope.

Biochemical heterogeneity of skeletal-muscle microsomal membranes. Membrane origin, membrane specificity and fibre types

Salviati, Giovanni; Volpe, Pompeo; Salvatori, Sergio; Betto, Romeo; Damiani, Ernesto; Margreth, Alfredo; Pasquali-Ronchetti, Ivonne
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/02/1982 EN
Relevância na Pesquisa
57.59618%
1. Microsomes were isolated from rabbit fast-twitch and slow-twitch muscle and were separated into heavy and light fractions by centrifugation in a linear (0.3–2m) sucrose density gradient. The membrane origin of microsomal vesicles was investigated by studying biochemical markers of the sarcoplasmic-reticulum membranes and of surface and T-tubular membranes, as well as their freeze-fracture properties. 2. Polyacrylamide-gel electrophoresis showed differences in the Ca2+-dependent ATPase/calsequestrin ratio between heavy and light fractions, which were apparently consistent with their respective origin from cisternal and longitudinal sarcoplasmic reticulum, as well as unrelated differences, such as peptides specific to slow-muscle microsomes (mol.wts. 76000, 60000, 56000 and 45000). 3. Freeze-fracture electron microscopy of muscle microsomes demonstrated that vesicles truly derived from the sarcoplasmic reticulum, with an average density of 9nm particles on the concave face of about 3000/μm2 for both fast and slow muscle, were admixed with vesicles with particle densities below 1000/μm2. 4. As determined in the light fractions, the sarcoplasmic-reticulum vesicles accounted for 84% and 57% of the total number of microsomal vesicles...

Changes in Membrane Lipid Composition during Saline Growth of the Fresh Water Cyanobacterium Synechococcus 6311 1

Huflejt, Margaret E.; Tremolieres, Antoine; Pineau, Bernard; Lang, Johanna K.; Hatheway, John; Packer, Lester
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/1990 EN
Relevância na Pesquisa
57.69707%
Growth of Synechococcus 6311 in the presence of 0.5 molar NaCl is accompanied by significant changes in membrane lipid composition. Upon transfer of the cells from a `low salt' (0.015 molar NaCl) to `high salt' (0.5 molar NaCl) growth medium at different stages of growth, a rapid decrease in palmitoleic acid (C16:1Δ9) content was accompanied by a concomitant increase in the amount of the two C18:1 acids (C18:1Δ9, C18:1Δ11), with the higher increase in oleic acid C18:1Δ9 content. These changes began to occur within the first hour after the sudden elevation of NaCl and progressed for about 72 hours. The percentage of palmitic acid (C16:0) and stearic acid (C18:0) remained almost unchanged in the same conditions. High salt-dependent changes within ratios of polar lipid classes also occurred within the first 72 hours of growth. The amount of monogalactosyl diacylglycerol (bilayer-destabilizing lipid) decreased and that of the digalactosyl diacylglycerol (bilayer-stabilizing lipid) increased. Consequently, in the three day old cells, the ratio of monogalactosyl diacylglycerol to digalactosyl diacylglycerol in the membranes of high salt-grown cells was about half of that in the membranes of low salt-grown cells. The total content of anionic lipids (phosphatidylglycerol and sulfoquinovosyl diacylglycerol) was always higher in the isolated membranes and the whole cells from high salt-grown cultures compared to that in the cells and membranes from low salt-grown cultures. All the observed rearrangements in the lipid environment occurred in both thylakoid and cytoplasmic membranes. Similar lipid composition changes...