Heterogenous lipid distribution among chlorophyll‐binding proteins of photosystem II in maize mesophyll chloroplasts

Abstract

Photosystem I1 membrane fractions from dark-adapted mesophyll chloroplasts of maize were solubilized in different concentrations of dodecyl P-D-maltoside. Chlorophyll-binding proteins from photosystem I1 were isolated either by ultracentrifugation on a sucrose gradient, or by flat bed isoelectric focusing and identified by gel electrophoresis analysis for their polypeptide composition. Lipid and fatty acid compositions were determined in complexes prepared by both methods and also in purified light-harvesting complex 11, in minor chlorophyll alb binding complexes 29, 26, 24, in photosystem I1 antennae (chlorophyll-protein complexes 43, 47) and in the photosystem I1 reaction centers chlorophyll-protein complexes. Comparative analysis of the results suggests that a true heterogeneity exists in the lipid class distribution among the different chlorophyll-protein complexes in this region of the photosynthetic membrane. Photosystem I1 core fractions prepared either by ultra-centrifugation on a sucrose gradient or by isoelectric focusing were found significantly enriched in monogalactosyldiacylglycerol ; fractionation of the photosystem I1 core in its components showed that it was the chlorophyll-protein complexes 43 and 47 which were mainly responsible for this enrichment. One of them, the chlorophyll-protein complex 47, was found containing monogalactos yldiacylglycerol and having a very high level of saturated fatty acids. The minor chlorophyll alb binding linkers (chlorophyll-protein complexes 24, 26 and 29) retain a largely higher amount of lipids than all other complexes and especially of highly unsaturated galactolipids.Concerning the main light-harvesting antenna (LHCII), it is demonstrated that phosphatidylglycerol is strongly linked to the complex if it cannot be detached at high detergent concentration, while many galactolipids (which nevertheless represent the major lipid classes) are lost. This main light-harvesting complex has been fractionated into several families by isoelectric focusing showing a marked difference in lipid and polypeptide composition. A spectacular increase in the phosphatidylglycerol content was observed in the fraction migrating near the anode and enriched in a 26-kDa polypeptide; but this result is difficult to interpret in physiological terms as it was shown that phosphatidylglycerol alone, because of its negative charge, also migrates toward the anode in isoelectric focusing.In photosynthesis, the two major functions of light-harvesting and electron transport occur in a thylakoid which is the predominant membrane in the plant leaf cell representing up to 80% of the total cellular membranes (Forde and Steer, 1976). Thylakoids are organized into two major functional domains. The appressed or granal membranes and the nonappressed or stromal membranes contain different complements of electron transport and binding complexes participating in the photosynthetic process. The lipid composition of the thylakoid is unique since it always contains four lipids never found in other cellular m...

The Xanthophyll Cycle Modulates the Kinetics of Nonphotochemical Energy Dissipation in Isolated Light-Harvesting Complexes, Intact Chloroplasts, and Leaves of Spinach1

“…Another explanation is that this complex so readily adopts the quenched state in vitro that xanthophylls are not limiting. This idea may relate to the greater hydrophobicity of the complex arising from the higher lipid-to-protein ratio (Tremolieres et al, 1994).…”

Glycerolipid transfer for the building of membranes in plant cells

“…Since these lipids are linked to specific structures of the photosystems, the lipid asymmetry of the thylakoids is likely to reflect the organisation of the photosynthetic machinery [24]. It has also been proposed that the asymmetry is preestablished in the inner envelope membrane due to the topography of lipid synthesising proteins and is transferred to thylakoids by membrane fusion [25].…”

Minor Antenna Proteins CP24 and CP26 Affect the Interactions between Photosystem II Subunits and the Electron Transport Rate in Grana Membranes of Arabidopsis

“…Grana partitions are made up essentially of proteins with very little lipids, which are tightly bound to photosynthetic complexes (Tremolieres et al, 1994). Previous work on negatively stained PSII membranes and cryo-EM analysis of negatively and unstained membranes has shown that tetrameric PSII particles protrude from the membrane plane, while Lhc particles are located in the dark background (Simpson, 1979).…”

“…PSII organized into ordered arrays restricts protein dynamics and limits the PQ diffusion. While the surface occupancy of randomly organized PSII and LHCII particles is 0.72 to 0.77 (Tremmel et al, 2003), ordered C2S2 arrays leave very little space in between particles (Morosinotto et al, 2006), thus allowing PQ diffusion only in boundary lipids tightly bound to membrane complexes (Tremolieres et al, 1994). This is fully consistent with the analysis of fluorescence induction curves (Figure 8; see Supplemental Figure 5 online), where the last phase (J-P), reflecting the reduction of acceptors downstream of PSII, primarily PQ, is delayed by five times in koCP24 with respect to the wild type.…”