The activities of glycerol-3 -phosphate acyltrans- ferase and l-monoacylglycerol-3-phosphate acyl- transferase, which are involved in the first steps in the biosynthesis of glycerolipids, are characterized in crude extracts of Anabaena variabilis Lem and Stumpf, 1984. A procedure was developed to purify simultaneously peroxisomes and mitochondria from spinach Spinacia oleracea L. The electron transport activity, measured in thylakoid membranes, showed increases ca. Antibody Studies A rather different approach to searching for specific lipid-protein interactions in photosynthetic mem- branes has been adopted by Radunz and his co- workers. Since this lipid is found in the cytoplasmic membrane but not in the chlorosome Olsen et al. The recent discovery showing that phosphorylation of lipids occurs in envelope membranes provides a new approach for understanding the role of chloroplast lipids in these processes. Phosphate Limitation The factors discussed above had only moderate effects on the membrane lipid composition of Rb.
Overall, sulfolipids are present in very high concentrations in diatoms. This series of multiauthored books spans topics from physics to agronomy, from femtosecond reactions to season long production, from the photophysics of reaction centers to the physiology of whole organisms, and from X-ray crys- tallography of proteins to the morphology of intact plants. . Many of our current ideas in these areas are based on a simple extrapolation of results obtained in studies carried out on purified thylakoid membrane lipids, or mixtures of such lipids. Phosphate uptake in the obligately marine fungus, Thraustochytrium roseum, is maximal at pH 7. The use of radiolabeled sulfate has enabled the detection of a number of unusual sulfur-containing lipids in algae. Detailed structural elucidation suggested that the aminolipid of Cb.
Patrick Williams performed on polyenoic molecular species show no unexpected features. Complete inhibitions were reached when maximum chloroplast swelling had occurred, i. The recent discovery showing that phosphorylation of lipids occurs in envelope membranes provides a new approach for understanding the role of chloroplast lipids in these processes. We showed that the effect of the herbicide begins only after 20h of exposure for the alga Scenedesmus vacuolatus based on both the optical density and algal cells size measurements. Biochim Biophys Acta 111: 41-55 Chapter 6 The Physical Properties of Thylakoid Membrane Lipids and Their Relation to Photosynthesis W. The phosphatidylglycerol- phosphate and phosphatidylserine synthases were partially purified and characterized in greater detail Radcliff et ah, 1989.
These results are discussed in terms of whether the breakdown of cytochrome b-559 high potential form can be related to the decrease in photochemical activities which characterizes chloroplast aging in vitro as well as in leaf senescence. Non-Specific Interactions In general, membranes with high protein contents such as chloroplast, mitochondrial and retinal rod membranes tend to have higher proportions of non- hilayer forming lipids. A: control without cross-linking reagent thylakoids 2. Thus, light acts synergetically towards the ageing process. Another polar lipid, that has been repeatedly suggested to play an importantrole inphotosynthetic membranes, is the sulfolipid sulfoquinovosyl diacylglycerol Barber and Gounaris, 1986. The gene for trans- carboxylase, which is a subunit of acetyl-CoA carboxylase, is encoded by the chloroplast genome. Within this range of concentration, the volume response of treated thylakoids to variation of osmolarity, an indirect mean of verifying the structural integrity of the membrane, was not altered.
Academic Press, New York Murata N, Sato N, Takahashi N and Hamazaki Y 1982 Compositions and positional distribution of fatty acids in phospholipids from leaves of chilling-sensitive and chilling- resistant plants. Biochim Biophys Acta 572: 376-381 Stanier Cohen-Bazire G 1988 Fine structure of cyanobacteria. Electronmicrographs illustrating typical structures found in such dispersions are presented in Eigs. A first step toward the elucidation of the regulatory mechanism would be the isolation of genes involved in the biosynthesis of specific lipids. Cultivars also presented maximal thylakoid membrane potential at different temperatures, with their values being 20. At each of the elongation steps, the reductive reactions are catalyzed by the reductases and dehydrase mentioned above.
When pancreatic phospholipase A2 had access either to the outer face or to both faces of the thylakoid membrane, either only part of or all the phospholipids, respectively, could be hydrolysed. A remarkable inhibitory effect of inorganic phosphate on chloroplast swelling is observed in the light, but not in the dark. Furthermore, employing the sqd genes of Rb. It is of interest that galactosyldiacylglycerols in chloroplast membranes were discovered only in the 1950s, although it is surely one of the the most abundant natural substances in the biosphere. Simultaneously, an increase in alpha-helix and a decrease particularly in the disordered conformations of protein secondary structures are observed.
The central role of diacylmonogalactosylglycerol in thermo- adaptation. The above distribution was found to be independent of the type of conditions used. The specific lipid composition of thylakoid membranes is regarded as being essential for the functions of these membranes, and alterations in the fatty acids of the membrane glycerolipids can affect the physical characteristics of the membranes and, consequently, the activities of the photosynthetic machinery. Pathway for synthesis of glycerolipids in chloroplasts. Ritter and Y opp 1993 investigated the effects of salinity on the lipid composition of the halophilic cyanobacterium Aphanothece halophytica.
It is generally believed that glycerolipids are asymmetrically distributed within the plane of the membrane. As described below, species in group 1 change both the extent of unsaturation and the chain length of fatty acids with alterations of growth temperatures, whereas species in the other groups change only the extent of unsaturation of fatty acids. Un traitement lumineux acclre ces phnomnes qui, probablement, sont associs des processus de dtrioration de l'appareil photosynthtique. The relative distribution of the four lipid classes, i. Polypeptides of 46, 19, and 12 kD were cross-linked to these complexes.
Although the major ornithine lipids of purple nonsulfur bacteria seem to be identical, the existence of additional ornithine containing lipids in purple nonsulfur bacteria has been reported e. Strains in the fourth group can introduce double bonds at the A6, A9, A 1 2 and A 1 5 o 3 positions ofC,g fatty acids at the sn-l position. The possible origin of galactolipid transversal asymmetry which appears very early during the biogenesis of oat thylakoid membranes is discussed. Our results show also that the 67 kD dark-phosphorylated protein is very likely to be a phosphoglucomutase, since its labelling was markedly reduced by the addition of exogenous glucose 1- or 6-phosphate. However, unambiguous evidence that the true electron donor for the envelope-bound fatty acid desaturase is indeed reduced ferredoxin, as proposed by Schmidt and Heinz 1990 a,b , is still lacking.
The biosynthesis of glycolipids in E. The effects of the concentration of nitrate in the medium on the fatty acid composition of four species of cyanobacteria were studied by Piorreck and Pohl 1984. Many of our current ideas in these areas are based on a simple extrapolation of results obtained in studies carried out on purified thylakoid membrane lipids, or mixtures of such lipids. Using careful washings and adequate lipid extraction procedures, we could ascertain that all hydrolysis products generated by phospholipase A2 were effectively removed from the thylakoid membrane by bovine serum albumin treatment. Secondly, the physical and chemical properties of Chlorella vulgaris and Chlorella protothecoides oil will be compared with diesel and biodiesel from other sources.