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1.
We are using fluorescence recovery after photobleaching (FRAP) to probe the dynamics of thylakoid membranes in vivo in cells of the cyanobacterium Synechococcus sp. PCC7942. We have shown previously that the light-harvesting phycobilisomes diffuse quite rapidly on the thylakoid membrane surface. However, the photosystem II core complexes appear completely immobile. This raises the possibility that all of the membrane integral protein complexes in the thylakoid membrane are locked into a rather rigid array. Alternatively, it is possible that photosystem II is specifically anchored in the membrane, with other membrane proteins able to diffuse around it. We have now resolved this question by studying the diffusion of a second integral membrane protein, the IsiA chlorophyll-binding protein. IsiA is induced under iron starvation and some other stress conditions. In iron-stressed cyanobacterial cells, a high proportion of chlorophyll fluorescence comes from IsiA. This makes it straightforward to examine the diffusion of IsiA by FRAP. We find that the complex is mobile with a mean diffusion coefficient of approximately 3 x 10(-11) cm(2) s(-1). Thus it is clear that some thylakoid membrane proteins are mobile and that there must be a specific anchor that prevents photosystem II diffusion. We discuss the implications for the structure and function of the cyanobacterial thylakoid membrane. 相似文献
2.
Lipid-protein interactions in thylakoid membranes, and in the subthylakoid membrane fractions containing either photosystem 1 or photosystem 2, have been studied by using spin-labeled analogues of the thylakoid membrane lipid components, monogalactosyldiacylglycerol, phosphatidylglycerol, and phosphatidylcholine. The electron spin resonance spectra of the spin-labeled lipids all consist of two components, one corresponding to the fluid lipid environment in the membranes and the other to the motionally restricted membrane lipids interacting directly with the integral membrane proteins. Spectral subtraction has been used to quantitate the fraction of the membrane lipids in contact with the membrane proteins and to determine the selectivity between the different lipid classes for the lipid-protein interaction. The fractions of motionally restricted lipid in the thylakoid membrane are 0.36, 0.39, and 0.53, for the spin-labeled monogalactosyldiacylglycerol, phosphatidylcholine, the phosphatidylglycerol, respectively. Spin-labeled monogalactosyldiacylglycerol exhibits very little preferential interaction over phosphatidylchline, which suggests that part of the role of monogalactosyldiacylglycerol in thylakoid membranes is structural, as is the case for phosphatidylcholine in mammalian membranes. Spin-labeled phosphatidylglycerol shows a preferential interaction over the corresponding monogalactosyldiacylglycerol and phosphatidylcholine analogues, in contrast to the common behavior of this lipid in mammalian systems. This pattern of lipid selectivity is preserved in both the photosystem 1 and photosystem 2 enriched subthylakoid membrane fractions. 相似文献
3.
Lipid membranes composed of monogalactosyldiacylglycerol (MGDG) and dimyristoylphosphatidylcholine (DMPC) were studied by means of NMR spectroscopy. The macroscopic phase behaviour was investigated by 31P NMR under stationary conditions, whereas microscopic properties such as segmental ordering were probed by two-dimensional 1H-13C separated local field experiments under magic-angle spinning conditions. Our results clearly show that ordering/disordering effects occur for the headgroups as well as for the acyl chains when the sample composition is varied. In particular, the 1H-13C dipolar couplings within the galactose headgroup of MGDG exhibited significant concentration dependence. 相似文献
4.
Castro V Dvinskikh SV Widmalm G Sandström D Maliniak A 《Biochimica et biophysica acta》2007,1768(10):2432-2437
Lipid membranes composed of monogalactosyldiacylglycerol (MGDG) and dimyristoylphosphatidylcholine (DMPC) were studied by means of NMR spectroscopy. The macroscopic phase behaviour was investigated by (31)P NMR under stationary conditions, whereas microscopic properties such as segmental ordering were probed by two-dimensional (1)H-(13)C separated local field experiments under magic-angle spinning conditions. Our results clearly show that ordering/disordering effects occur for the headgroups as well as for the acyl chains when the sample composition is varied. In particular, the (1)H-(13)C dipolar couplings within the galactose headgroup of MGDG exhibited significant concentration dependence. 相似文献
5.
The Na+ requirement for photosynthesis and its relationship to dissolved inorganic carbon (DIC) concentration and Li+ concentration was examined in air-grown cells of the cyanobacterium Synechococcus leopoliensis UTEX 625 at pH 8. Analysis of the rate of photosynthesis (O2 evolution) as a function of Na+ concentration, at fixed DIC concentration, revealed two distinct regions to the response curve, for which half-saturation values for Na+ (K½[Na+]) were calculated. The value of both the low and the high K½(Na+) was dependent upon extracellular DIC concentration. The low K½(Na+) decreased from 1000 micromolar at 5 micromolar DIC to 200 micromolar at 140 micromolar DIC whereas over the same DIC concentration range the high K½(Na+) decreased from 10 millimolar to 1 millimolar. The most significant increases in photosynthesis occurred in the 1 to 20 millimolar range. A fraction of total photosynthesis, however, was independent of added Na+ and this fraction increased with increased DIC concentration. A number of factors were identified as contributing to the complexity of interaction between Na+ and DIC concentration in the photosynthesis of Synechococcus. First, as revealed by transport studies and mass spectrometry, both CO2 and HCO3− transport contributed to the intracellular supply of DIC and hence to photosynthesis. Second, both the CO2 and HCO3− transport systems required Na+, directly or indirectly, for full activity. However, micromolar levels of Na+ were required for CO2 transport while millimolar levels were required for HCO3− transport. These levels corresponded to those found for the low and high K½(Na+) for photosynthesis. Third, the contribution of each transport system to intracellular DIC was dependent on extracellular DIC concentration, where the contribution from CO2 transport increased with increased DIC concentration relative to HCO3− transport. This change was reflected in a decrease in the Na+ concentration required for maximum photosynthesis, in accord with the lower Na+-requirement for CO2 transport. Lithium competitively inhibited Na+-stimulated photosynthesis by blocking the cells' ability to form an intracellular DIC pool through Na+-dependent HCO3− transport. Lithium had little effect on CO2 transport and only a small effect on the size of the pool it generated. Thus, CO2 transport did not require a functional HCO3− transport system for full activity. Based on these observations and the differential requirement for Na+ in the CO2 and HCO3− transport system, it was proposed that CO2 and HCO3− were transported across the membrane by different transport systems. 相似文献
6.
M D Mamedov H Hayashi H Wada P S Mohanty G C Papageorgiou N Murata 《FEBS letters》1991,294(3):271-274
Glycinebetaine (betaine), an osmoregulant in halophilic plants, stabilized the evolution of oxygen and the synthesis of ATP by thylakoid membranes from the cyanobacterium Synechocystis PCC6803 when it was present during the preparation and incubation of the thylakoid membranes. Moreover, betaine enhanced the evolution of oxygen and the synthesis of ATP when present during assays. When betaine at 1.0 M was present during the preparation of thylakoid membranes and during the measurement of activity, the rate of evolution of oxygen was equivalent to that of intact cells. 相似文献
7.
Structure and functional role of supercomplexes of IsiA and Photosystem I in cyanobacterial photosynthesis 总被引:1,自引:0,他引:1
Kouril R Arteni AA Lax J Yeremenko N D'Haene S Rögner M Matthijs HC Dekker JP Boekema EJ 《FEBS letters》2005,579(15):3253-3257
Cyanobacteria express large quantities of the iron stress-inducible protein IsiA under iron deficiency. IsiA can assemble into numerous types of single or double rings surrounding Photosystem I. These supercomplexes are functional in light-harvesting, empty IsiA rings are effective energy dissipaters. Electron microscopy studies of these supercomplexes show that Photosystem I trimers bind 18 IsiA copies in a single ring, whereas monomers may bind up to 35 copies in two rings. Work on mutants indicates that the PsaF/J and PsaL subunits facilitate the formation of closed rings around Photosystem I monomers but are not obligatory components in the formation of Photosystem I-IsiA supercomplexes. 相似文献
8.
David O. Hall Sergei A. Markov Yoshitomo Watanabe K. Krishna Rao 《Photosynthesis research》1995,46(1-2):159-167
Natural photosynthesis may be adapted to advantage in the development of clean energy technologies. Efficient biocatalysts that can be used in solar energy conversion technologies are the cyanobacteria. Photobioreactors incorporating cyanobacteria have been used to demonstrate (a) the production of hydrogen gas, (b) the assimilation of CO2 with the production of algal biomass, (c) the excretion of ammonium, and (d) the removal of nitrate and phosphate from contaminated waters.Abbreviations Chl
chlorophyll
- DW
dry weight
- MSX
L-methionine-D-L-sulphoximine
- PAR
photosynthetically active radiation
- PU
polyurethane
- PV
polyvinyl
- PVC
polyvinylchloride 相似文献
9.
10.
ML DeMarco 《Biochemistry》2012,51(29):5725-5732
Characterizing the structure-function relationships of glycolipids in lipid membranes is a challenging endeavor. Glycolipid structure is rarely, if ever, a unique low-energy conformer, but an ensemble of dynamic states, which vary in their presentation of binding epitopes. The modulation of binding epitopes not only is an internal process but also is influenced by external factors such as glycolipid clustering and fluctuations in and composition of the fluid membrane environment. As with other glyco-conjugates, three-dimensional structural elucidation has relied heavily on nuclear magnetic resonance spectroscopy and computational modeling. Discrete conformational states can be discerned from motion-averaged experimental data by employing independent molecular dynamics simulations. Using model membranes such as micelles, bicelles, and bilayers, we can approximate the effect of their biological environment and quantify cell-surface presentation. 相似文献
11.
Kurt A. Santarius 《Physiologia plantarum》1984,61(4):591-598
Thylakoids isolated from spinach leaves ( Spinacia oleracea L. cv. Monatol) were exposed to variable low temperatures under non-freezing conditions. After incubation, changes in the activities of several photochemical reactions and physical properties of the membranes were measured at room temperature.
Cyclic photophosphorylation was strictly dependent on the temperature and the electrolyte concentration: decrease in temperature and increase in NaCl concentration enhanced membrane damage. Inactivation of photophosphorylation was accompanied by stimulation of non-cyclic electron transport, increase in proton permeability and decrease in δpH. When dicyclohexylcarbodiimide was added, the proton gradient became completely restored. The temperature- and salt-dependent breakdown of photophosporylation was closely related to the release of the chloroplast coupling factor (CF1 ) from the membranes. The addition of Mg2+ , very low concentrations of ATP or ADP, or higher concentrations of low-molecular-weight polyols prior to temperature treatment prevented thylakoid damage.
The data indicate that inactivation of photophosphorylation of thylakoids at low temperatures is determined to a considerable extent by the cold lability of the CF1 . As a consequence, it must be concluded that damage of biomembranes caused by freezing is not due solely to changes resulting from the ice formation but additionally by temperature-dependent alterations of cold-labile proteins. Moreover, the data explain the mechanism of non-colligative cryoprotection of isolated thylakoid membranes. 相似文献
Cyclic photophosphorylation was strictly dependent on the temperature and the electrolyte concentration: decrease in temperature and increase in NaCl concentration enhanced membrane damage. Inactivation of photophosphorylation was accompanied by stimulation of non-cyclic electron transport, increase in proton permeability and decrease in δpH. When dicyclohexylcarbodiimide was added, the proton gradient became completely restored. The temperature- and salt-dependent breakdown of photophosporylation was closely related to the release of the chloroplast coupling factor (CF
The data indicate that inactivation of photophosphorylation of thylakoids at low temperatures is determined to a considerable extent by the cold lability of the CF
12.
13.
J. Kenneth Hoober Richard A. White Dawn B. Marks Jerome L. Gabriel 《Photosynthesis research》1994,39(1):15-31
Recent results obtained by electron microscopic and biochemical analyses of greening Chlamydomonas reinhardtii y1 suggest that localized expansion of the plastid envelope is involved in thylakoid biogenesis. Kinetic analyses of the assembly of light-harvesting complexes and development of photosynthetic function when degreened cells of the alga are exposed to light suggest that proteins integrate into membrane at the level of the envelope. Current information, therefore, supports the earlier conclussion that the chloroplast envelope is a major biogenic structure, from which thylakoid membranes emerge. Chloroplast development in Chlamydomonas provides unique opportunities to examine in detail the biogenesis of thylakoids.Abbreviations Rubisco
ribulose bisphosphate carboxylase/oxygenase
- CAB
Chl a/b-binding (proteins)
- Chlide
chlorophyllide
- LHC I
light-harvesting complex of PS I
- LHC II
light-harvesting complex of PS II
- Pchlide
protochlorophyllide 相似文献
14.
Environmental effects on acidic lipids of thylakoid membranes 总被引:6,自引:0,他引:6
The contents of the chloroplast acidic lipids, SQDG (sulphoquinovosyldiacylglycerol) and PG (phosphatidylglycerol), were reduced in the cells of Chlamydomonas reinhartdtii with exposure to sulphur- or phosphorus-source limitation, respectively. The decrease in the content of one acidic lipid was accompanied by an increase in the content of the other acidic lipid, which resulted in the maintenance of a certain level of total acidic lipids of chloroplast membranes. On the other hand, the content of each acidic lipid was little affected by temperature stresses during cell growth. 相似文献
15.
Changes in the conformation of spinach thylakoid membranes were monitored in 5-doxyl stearic acid (SAL)-treated thylakoid
membranes in the presence of various anions (Cl−, Br−, I−, NO2
−, SO4
2−, PO4
3−). The presence of anions made the thylakoid membrane more fluid. The extent of change in membrane fluidity differed with
different anion and was reversible. 相似文献
16.
The light-harvesting complex II (LHCII) is the main energy absorber for photosynthesis in green plants, and its translocation between photosystems I and II is the primary means of energy redistribution between them. Using single-particle tracking, we performed the first measurement of the mobility of LHCII in the photosynthetic membranes in both the nonphosphorylated and the phosphorylated (P-LHCII) conformations. These are part of an important, reversible, energy re-equilibration process called the state transition. We found that the population of P-LHCII in unappressed membranes is more mobile than the population of non-P-LHCII from the same regions. 相似文献
17.
Deuterium NMR studies of the interactions of polyhydroxyl compounds and of glycolipids with lipid model membranes 总被引:1,自引:0,他引:1
The physical properties of bilayers composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) in the presence of four water-soluble polyhydroxyl compounds, trehalose, sorbitol, glycerol, and ethyleneglycol, and three neutral glycolipids - monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG) and nonhydroxy fattyacyl-cerebrosides (NHFA-Cer) - were investigated using 2H-NMR. All four polyhydroxyl compounds induced small, but comparable concentration-dependent changes in the choline headgroup conformation which were consistent with the presence of a small negative charge being conferred upon the bilayer surface. The latter may be explained by dipolar interactions brought about by changes in the long-range order of the water layer at the membrane surface. Trehalose had a small ordering effect on the hydrophobic interior of the membrane while ethyleneglycol induced a disordering, at both the head group level and in the hydrophobic interior. The presence of high amounts of carbohydrate at the membrane surface was ensured when POPC was mixed with various proportions of one of three glycolipids, MGDG, DGDG and NHFA-Cer. In these cases the conformation of the choline headgroup was only marginally altered when not masked by macroscopic phase changes. The headgroup conformational changes observed in the presence of any of the above-mentioned compounds were modest in comparison to the effects induced by charged substances. 相似文献
18.
Derek Marsh 《Chemistry and physics of lipids》2010,163(7):667-677
Data on the molecular volumes of phospholipids and glycolipids in membranes are collected together in order to determine the contributions from the component groups, for as wide a range of lipids as possible, including sphingolipids. Wherever possible, the volumes of the methylene groups in the lipid chains are established from the dependence on chain length at fixed temperature in a given phase. In this way, it is also possible to determine the constant contribution from cis double bonds in the chains of monoenoic unsaturated phosphatidylcholines, and the volume of the branched methyl groups in isoacyl phosphatidylcholines. Issues concerning separation of contributions from the polar head groups from those of the chain terminal methyl groups are discussed. Molecular volumes of lipids in crystals are also analysed to provide information on head-group packing that can be compared with the situation in membranes, and used to set limits on the relative contributions from polar groups and terminal methyl groups. Comparisons are made with volumetric analyses based on diffraction studies of bilayers of single lipids. The parameters derived can be used to estimate molecular volumes of lipids for which dilatometric or densitometric data are lacking. Lipid volumes are determining parameters for lipid dynamics, membrane partitioning and permeation of solutes, and are essential quantities for the structural analysis of lipid membranes. 相似文献
19.
Phosphatidylglycerol is essential for the development of thylakoid membranes in Arabidopsis thaliana
Phosphatidylglycerol is a ubiquitous phospholipid in the biological membranes of many organisms. In plants, phosphatidylglycerol is mainly present in thylakoid membranes and has been suggested to play specific roles in photosynthesis. Here, we have isolated two T-DNA tagged lines of Arabidopsis thaliana that have a T-DNA insertion in the PGP1 gene encoding a phosphatidylglycerolphosphate synthase involved in the biosynthesis of phosphatidylglycerol. In homozygous plants of the T-DNA tagged lines, the PGP1 gene was completely disrupted. The growth of these knockout mutants was dependent on the presence of sucrose in the growth medium, and these plants had pale yellow-green leaves. The leaves of the mutants had remarkably large intercellular spaces due to the reduction in the number of mesophyll cells. The development of chloroplasts in the leaf cells was severely arrested in the mutants. Mesophyll cells with chloroplast particles are only found around vascular structures, whereas epidermal cells are enlarged but largely conserved. The content of phosphatidylglycerol in the mutants was reduced to 12% of that of the wild type. These results demonstrate that PGP1 plays a major role in the biosynthesis of phosphatidylglycerol in chloroplasts, and that phosphatidylglycerol is essential for the development of thylakoid membranes in A. thaliana. 相似文献
20.
Dirk Schneider Eva Fuhrmann Ingeborg Scholz Wolfgang R Hess Peter L Graumann 《BMC cell biology》2007,8(1):39