Self-assembly of large, ordered lamellae from non-bilayer lipids and integral membrane proteins in vitro (original) (raw)
Related papers
Biochemistry, 1998
We studied the role of added thylakoid lipids in the light-induced reversible structural changes in isolated macroaggregates of the main light-harvesting chlorophyll a/b complex of photosystem II (LHCII). Loosely stacked lamellar macroaggregates were earlier shown to undergo light-induced reversible structural changes and changes in the photophysical pathways, which resembled those in thylakoid membranes exposed to excess light [Barzda, V., et al. (1996) Biochemistry 35, 8981-8985]. This structural flexibility of LHCII depends critically on the lipid content of the preparations [Simidjiev, I., et al. (1997) Anal. Biochem. 250, 169-175]. It is now reported that lamellar aggregates of LHCII are capable of incorporating substantial amounts of different thylakoid lipids. The long-range order of the chromophores is retained, while the ultrastructure of the lipid-protein macroaggregates can be modified significantly. Addition of thylakoid lipids to the preparations significantly enhances the ability of the LHCII macroaggregates to undergo light-induced structural changes. The lipid environment of the LHCII complexes therefore plays a significant role in determining the structural flexibility of the macroaggregates. As concerns the mechanism of these changes, it is proposed that the absorption of light and the dissipation of its energy in the macrodomains induces thermal fluctuations which bring about changes in the shape or in the stacking interactions of the membranes, this in turn affecting the long-range order of the embedded chromophores. In thylakoids, a similar mechanism is likely to explain the light-induced structural changes which are largely independent of the photochemical activity of the membranes.
Biochemistry, 1998
We studied the role of added thylakoid lipids in the light-induced reversible structural changes in isolated macroaggregates of the main light-harvesting chlorophyll a/b complex of photosystem II (LHCII). Loosely stacked lamellar macroaggregates were earlier shown to undergo light-induced reversible structural changes and changes in the photophysical pathways, which resembled those in thylakoid membranes exposed to excess light [Barzda, V., et al. (1996) Biochemistry 35, 8981-8985]. This structural flexibility of LHCII depends critically on the lipid content of the preparations [Simidjiev, I., et al. (1997) Anal. Biochem. 250, 169-175]. It is now reported that lamellar aggregates of LHCII are capable of incorporating substantial amounts of different thylakoid lipids. The long-range order of the chromophores is retained, while the ultrastructure of the lipid-protein macroaggregates can be modified significantly. Addition of thylakoid lipids to the preparations significantly enhances the ability of the LHCII macroaggregates to undergo light-induced structural changes. The lipid environment of the LHCII complexes therefore plays a significant role in determining the structural flexibility of the macroaggregates. As concerns the mechanism of these changes, it is proposed that the absorption of light and the dissipation of its energy in the macrodomains induces thermal fluctuations which bring about changes in the shape or in the stacking interactions of the membranes, this in turn affecting the long-range order of the embedded chromophores. In thylakoids, a similar mechanism is likely to explain the light-induced structural changes which are largely independent of the photochemical activity of the membranes.
Journal of Biosciences, 1990
Aqueous dispersions of lipids isolated from spinach chloroplast membranes were studied by electron microscopy after negative staining with phosphotungstic acid. Influence of low temperature (5°C for 24 h) was also investigated. It was observed that when contacted with water, these lipids, as such, formed multilamellar structures. Upon sonication, these multilamellar structures gave rise to a clear suspension of unilamellar vesicles varying in size (diameter) between 250 and 750 Å. When samples of sonicated unilamellar vesicles were stored at 5°C for 24 h or more, they revealed a variety of lipid aggregates including liposomes, cylindrical rods (about 100 Å wide and up to 3600 Å long), and spherical micellar structures (100-200 Å in diameter)-thus indicating phase separation of lipids.
Aqueous dispersions of lipids isolated from spinach chloroplast membranes were studied by electron microscopy after negative staining with phosphotungstic acid. Influence of low temperature (5°C for 24 h) was also investigated. It was observed that when contacted with water, these lipids, as such, formed multilamellar structures. Upon sonication, these multilamellar structures gave rise to a clear suspension of unilamellar vesicles varying in size (diameter) between 250 and 750 Å. When samples of sonicated unilamellar vesicles were stored at 5°C for 24 h or more, they revealed a variety of lipid aggregates including liposomes, cylindrical rods (about 100 Å wide and up to 3600 Å long), and spherical micellar structures (100-200 Å in diameter)-thus indicating phase separation of lipids.
The Plant Cell, 2013
In this study, we analyzed multibilayer lipid-protein membranes composed of the photosynthetic light-harvesting complex II (LHCII; isolated from spinach [Spinacia oleracea]) and the plant lipids monogalcatosyldiacylglycerol and digalactosyldiacylglycerol. Two types of pigment-protein complexes were analyzed: those isolated from dark-adapted leaves (LHCII) and those from leaves preilluminated with high-intensity light (LHCII-HL). The LHCII-HL complexes were found to be partially phosphorylated and contained zeaxanthin. The results of the x-ray diffraction, infrared imaging microscopy, confocal laser scanning microscopy, and transmission electron microscopy revealed that lipid-LHCII membranes assemble into planar multibilayers, in contrast with the lipid-LHCII-HL membranes, which form less ordered structures. In both systems, the protein formed supramolecular structures. In the case of LHCII-HL, these structures spanned the multibilayer membranes and were perpendicular to the membrane plane, whereas in LHCII, the structures were lamellar and within the plane of the membranes. Lamellar aggregates of LHCII-HL have been shown, by fluorescence lifetime imaging microscopy, to be particularly active in excitation energy quenching. Both types of structures were stabilized by intermolecular hydrogen bonds. We conclude that the formation of trans-layer, rivet-like structures of LHCII is an important determinant underlying the spontaneous formation and stabilization of the thylakoid grana structures, since the lamellar aggregates are well suited to dissipate excess energy upon overexcitation.
Analytical Biochemistry, 1997
centers. The pigment-protein complexes are found in a Isolation of LHCII, the light-harvesting chlorophyll lipid environment of the thylakoid membranes in an ora/b complex of photosystem II, based on the procedure dered fashion. The major light-harvesting antenna comdescribed by Krupa et al. (1987, Plant Physiol. 84, 19-plex associated with photosystem II is LHCII, 1 the main 24), was optimized for obtaining purified lamellar agchlorophyll a/b complex. It is one of the few membrane gregates with long-range chiral order and structural proteins with well-determined crystallographic structure flexibility (the capability of undergoing light-induced (1). Its polypeptide chain and pigment composition as well reversible structural changes). By varying the concenas the lipid content have been investigated in depth in tration of the detergent Triton X-100 for the solubilizathe past decade (1-4, for recent review see 5). In addition tion of thylakoid membranes, we obtained four types to its primary role, harvesting the light and transferring of LHCII aggregates: (i) With low detergent concentrathe excitation energy to the reaction centers, LHCII has tion, £0.6% (v/v), the aggregates contained lipids in been proposed to play an important role in mediating the high amount. These preparations with Chl a/b ratios stacking of membranes (6). LHCII also participates in of about 1.4 contained minor antenna complexes with different regulatory photophysical processes in the ana fingerprint of an additional CD band at (/) 505 nm; tenna (7, 8). This type of regulation requires a flexibility they formed disordered lamellae and exhibited no or in the molecular organization of the antenna system. weak psi-type CD bands (psi, polymerization-or salt-LHCII has been shown to play an important role in the induced), which did not possess the ability to undergo assembly of chirally organized macrodomains of photosyslight-induced changes (DCD). (ii) At the optimal contem II (PSII) particles, a mechanism held responsible for centration, around 0.7 { 0.1% (v/v), the detergent rethe spatial separation of the two photosystems (9, 10).
The non-bilayer lipid MGDG stabilizes the major light-harvesting complex (LHCII) against unfolding
Scientific Reports
In the photosynthetic apparatus of plants a high proportion of LHCII protein is needed to integrate 50% non-bilayer lipid MGDG into the lamellar thylakoid membrane, but whether and how the stability of the protein is also affected is not known. Here we use single-molecule force spectroscopy to map the stability of LHCII against mechanical unfolding along the polypeptide chain as a function of oligomerization state and lipid composition. Comparing unfolding forces between monomeric and trimeric LHCII demonstrates that the stability does not increase significantly upon trimerization but can mainly be correlated with specific contact sites between adjacent monomers. In contrast, unfolding of trimeric complexes in membranes composed of different thylakoid lipids reveals that the non-bilayer lipid MGDG substantially increases the mechanical stability of LHCII in many segments of the protein compared to other lipids such as DGDG or POPG. We attribute these findings to steric matching of conically formed MGDG and the hourglass shape of trimeric LHCII, thereby extending the role of nonbilayer lipids to the structural stabilization of membrane proteins in addition to the modulation of their folding, conformation and function.
Febs Letters, 1982
Photosynthetic membranes contain considerable regions of high surface curvature, notably at their margins, where the average radius of curvature is about 10 nm. The proportion of total membrane lipid in the outer and inner thylakoid margin monolayers is estimated at 21% and 13%, respectively. The major thylakoid lipid, monogalactosyldiacylglycerol, is roughly cone-shaped and will not form complete lamellar bilayer phases, even in combination with other thylakoid lipids. It is proposed that this galactolipid plays a role in: (a) stabilising regions of concave curvature in thylakoids; and (b) packaging hydrophobic proteins in planar bilayer regions by means of inverted micelles. This model predicts substantial asymmetries in the distribution of lipids both across and along the thylakoid bilayer plane.
Physiologia Plantarum, 2017
The study investigated the effect of the thylakoid membrane lipids monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulphoquinovosyldiacylglycerol (SQDG) and phosphatidylglycerol (PG) on the structure of two algal light-harvesting complexes (LHC). In contrast to higher plants whose thylakoid membranes are characterized by an enrichment of the neutral galactolipids MGDG and DGDG, both the green alga Mantoniella squamata and the centric diatom Thalassiosira pseudonana contain membranes with a high content of the negatively charged lipids SQDG and PG. The algal thylakoids do not show the typical grana-stroma differentiation of higher plants but a regular arrangement. To analyze the effect of the membrane lipids, the FCP complex of T. pseudonana and the LHC of M. squamata (MLHC) were prepared by successive cation precipitation using Triton X-100 as detergent. With this method, it is possible to isolate LHCs with a reduced amount of associated lipids in an aggregated state. The results from 77 K fluorescence and photon correlation spectroscopy show that neither the neutral galactolipids nor the negatively charged lipids are able to significantly alter the aggregation state of the FCP or the MLHC. This is in contrast to higher plants where SQDG and PG lead to a strong disaggregation of the LHCII whereas MGDG and DGDG induce the formation of large macro