15 research outputs found
EPR study of thylakoid membrane dynamics in mutants of the carotenoid biosynthesis pathway of Synechocystis sp. PCC6803
EPR spectroscopy using 5-doxylstearic acid (5-SASL) and 16-doxylstearic acid (16-SASL) spin probes was used to study the fluidity of thylakoid membranes. These were isolated from wild type Synechocystis and from several mutants in genes encoding selected enzymes of the carotenoid biosynthesis pathway and/or acyl-lipid desaturases. Cyanobacteria were cultivated at 25°C and 35°C under different light regimes: photoautotrophically (PAG) and/or in light-activated heterotrophic conditions (LAHG). The relative fluidity of membranes was estimated from EPR spectra based on the empirical outermost splitting parameter in a temperature range from 15°C to 40°C. Our findings demonstrate that in native thylakoid membranes the elimination of xanthophylls decreased fluidity in the inner membrane region under optimal growth conditions (25°C) and increased it under sublethal heat stress (35°C). This indicated that the overall fluidity of native photosynthetic membranes in cyanobacteria may be influenced by the ratio of polar to non-polar carotenoid pools under different environmental conditions
Regulatory role of photosystem I trimerization on light-dependent reactions of photosynthesis in cyanobacterium Synechocystis PCC6803
The role of carotenoids in the protection and assembly of the photosynthetic apparatus in a model unicellular cyanobacteria Synechocystis PCC 6803
The effect of solvent on the optical properties of myxoxanthophyll from Synechocystis sp. PCC6803
Effect of growth temperature on biosynthesis and accumulation of carotenoids in cyanobacterium Anabaena sp. PCC 7120 under diazotrophic conditions
Photosystem I oligomerization affects lipid composition in Synechocystis sp. PCC 6803
In cyanobacteria, increasing growth temperature decreases lipid unsaturation and the ratio of monomer/trimer photosystem I (PSI) complexes. In the present study we applied Fourier-transform infrared (FTIR) spectroscopy and lipidomic analysis to study the effects of PSI monomer/oligomer ratio on the physical properties and lipid composition of thylakoids. To enhance the presence of monomeric PSI, a Synechocystis sp. PCC6803/ΔpsaL mutant strain (PsaL) was used which, unlike both trimeric and monomeric PSI-containing wild type (WT) cells, contain only the monomeric form. The protein-to-lipid ratio remained unchanged in the mutant but, due to an increase in the lipid disorder in its thylakoids, the gel to liquid-crystalline phase transition temperature (Tm) is lower than in the WT. In thylakoid membranes of the mutant, digalactosyldiacylglycerol (DGDG), the most abundant bilayer-forming lipid is accumulated, whereas those in the WT contain more monogalactosyldiacylglycerol (MGDG), the only non-bilayer-forming lipid in cyanobacteria. In PsaL cells, the unsaturation level of sulphoquinovosyldiacylglycerol (SQDG), a regulatory anionic lipid, has increased. It seems that merely a change in the oligomerization level of a membrane protein complex (PSI), and thus the altered protein-lipid interface, can affect the lipid composition and, in addition, the whole dynamics of the membrane. Singular value decomposition (SVD) analysis has shown that in PsaL thylakoidal protein-lipid interactions are less stable than in the WT, and proteins start losing their native secondary structure at much milder lipid packing perturbations. Conclusions drawn from this system should be generally applicable for protein-lipid interactions in biological membranes