Phosphatidylglycerol Acid Research Articles

Phospholipid composition of chlorophyll-free mitochondria isolated via protoplasts from oat mesophyll cells.

Mitochondria were isolated from oat primary leaves via mesophyll protoplasts and subjected to phospholipid analysis. In mesophyll cells mitochondria account for only small proportions of cellular phospholipids (in the order of 5%) and proteins (in the order of 2%). Contamination by lipids from other membranes was insignificant as indicated by the absence or very low levels of chlorophyll, galactolipids and steryl glycosides. The absence of 3-trans-hexadecenoic acid in phosphatidylglycerol from mitochondria of green cells serves an an additional criterion of purity. The phospholipid mixture extracted from these mitochondria resembles phospholipids in mitochondria from non-green tissues regarding composition as well as fatty acid profiles. Therefore, mitochondria maintain a rather constant lipid profile and in contrast to plastids do not respond at this level to differences in the physiological status of their housing cell. Palmitic acid in mitochondrial phosphatidylcholine and phosphatidylethanolamine is primarily localized at the C-1 position of the glycerol moiety. Two enzymatic activities so far not described in mitochondria, formation of acylgalactosyl diacylglycerol and hydrolysis of acyl-CoA, were found in the purified mitochondrial fraction.

The positional distribution of a series of positional isomers of cis-octadecenoic acid in phosphatidylglycerol from Acholeplasma laidlawii B

The positional distributions of a series of fifteen positional isomers of cis-octadecenoic acid in the phosphatidylglycerol synthesized by Acholeplasma laidlawii B were determined. The specificity for the 2-position generally increased (and that for the 1-position decreased) as the position of the double bond moved from the methyl terminus toward the carbonyl group of the hydrocarbon chain. The Δ 5 and Δ 6 cis-octadecenoates, however, were exceptional in exhibiting a much lower 2-positional specificity than the adjacent members in this series. The positional specificities of the Δ 5, Δ 6 and Δ 9 through Δ 17- cis-octadecenoic acids correlated well with the melting behavior (gel to liquid-crystalline phase transition temperatures) of the corresponding 1,2-dioctadecenoyl phosphatidylcholines. In contrast, the Δ 3 and Δ 4, and the Δ 7 and Δ 8-octadecenoate isomers exhibited specificities for position 2 which are markedly and moderately greater, respectively, than would be predicted from the melting behavior of the corresponding phosphatidylcholines. The fatty acid specificity of the enzyme system catalyzing the acylation of sn-glycerol-3-phosphate in this organism is such that the biosynthesis of membrane glycerolipids having a high degree of physicochemical homogeneity is generally promoted, particularly when naturally occurring mono- and polyunsaturated fatty acids are utilized.

Lipid metabolism in green leaves of developing monocotyledons

Lipid synthesis was studied in successive leaf sections from the base to the tip of developing barley (Hordeum vulgare L.), maize (Zea mays L.), rye grass (Lolium perenne L.) and wheat (Triticum aestivum L.) leaves. The endogenous levels of acyl lipids and their constituent fatty acids from the same leaf sections were also analysed. The principle chloroplast acyl lipids showed a relative increase in amount with the age of the leaf section. Their content of α-linolenic acid also increased whereas there was little change in the amount of this acid in phosphatidylcholine and phosphatidylethanolamine, which are primarily non-chloroplastic. The content of trans-3-hexadecenoic acid in phosphatidylglycerol increased approximately 20-fold between the youngest (basal) and oldest (distal) leaf sections.The incorporation of [(14)C]acetate was always high into monogalactosyldiacylglycerol, phosphatidylcholine and the neutral lipid (mainly pigments) fractions. With increasing age, the neutral lipids were less well labelled. In three of the plant species but not in barley, phosphatidylglycerol was heavily labelled. Monogalactosyldiacylglycerol usually contained the highest amount of radioactivity in the middle leaf sections. Apart from these generalisations, each plant type had its own specific pattern of radiolabelling.

Structure and assembly of lipid-containing viruses, with special reference to bacteriophage PM2 as one type of model system.

The simpler lipid-containing viruses (influenza, Semliki Forest, PM2) may have a phospholipid bilayer sandwiched between an outer shell of protein and an internal nucleocapsid possessing helical or icosahedral symmetry. Extensive physical and chemical studies have enabled us to form a more detailed picture of the structure of bacteriophage PM2 and controlled stepwise degradation of the virion has helped us to localize the four viral proteins. The surface protein (II) of PM2 is basic and interacts with the acidic phosphatidylglycerol of the bilayer to stabilize the membrane. The nucleocapsid protein (III) has proteolipid characteristics and may interact with the phospholipids in a hydrophobic fashion. The spikes are formed from protein I and the fourth protein (IV) is closely associated with the DNA. It is possible to reassemble the virus by reversing the degradation steps. Assembly has been especially useful in revealing the processes whereby the proteins and lipids interact to form the bilayer. Furthermore, results of in vivo studies of phospholipid synthesis and both in vivo and in vitro studies of viral protein synthesis have enabled us to form a reasonably complete picture of the biosynthesis of PM2.

Galactolipid Synthesis in Vicia faba Leaves

The labeling kinetics of the fatty acids of phosphatidylcholine (PC), phosphatidylglycerol (PG), monogalactosyldiglyceride (MGDG), and digalactosyldiglyceride (DGDG) were examined after (14)CO(2) feeding and incubation of leaf discs of Vicia faba over 72 hours in continuous light. The results indicate a rapid accumulation and turnover of radioactivity into PC and PG fatty acids (oleic acid in PC and oleic and palmitic acids in PG). Radioactivity accumulates in MGDG and DGDG fatty acids much more slowly and continuously over 72 hours. Most of this activity is found in linoleic and linolenic acids; very little activity is found in the more saturated fatty acids. Little or no desaturation occurs in situ in conjunction with the galactolipids. The results suggest that PC and PG may act as "carriers" for MGDG and DGDG fatty acid synthesis. Analyses of the labeling patterns of the molecular species of MGDG after (14)CO(2) and (14)C-acetate feeding confirm that MGDG is formed by galactosylation of a preformed diglyceride containing predominantly unsaturated fatty acids.

Effect of Preparation Method on the Induction of (Sodium + Potassium) –Activated Adenosine Triphosphalase from Sugar Beet Root and its Lipid Composition

AbstractThe (Na++K+)–stimulation of the ATPase activity in a paniculate fraction from sugar beet roots was compared after inducing treatments with dithiothreitol (DTT), cystein or deoxycholate (DOC). Protection of SH groups by cystein or DTT increased the specific activity at the optimal Na: K ratio (25 :25 mM) with a factor of about 5 as compared to the untreated fraction, and with a factor of about 3 as compared to particles treated with DOC. DTT acted chiefly at the optimum ratio of Na : K (25 :25 mM), whereas a less specific stimulation at any proportion of the couple Na : K was observed after treatment with DOC or cystein. A combined treatment (DOC + DTT) led to inactivation of the DTT effect.Treatment with DTT resulted in a loss of lipids, which were replaced by water, but otherwise little swelling took place. The loss of lipids was almost exclusively due to loss of phospholipids, and among these the zwitterkonic phos–phatidyl choline and phosphatidyl ethanolamine were affected more than the acidic phosphatidyl glycerol or phosphatidyl inositol. The sulfolipid was maintained within the particles. The combined treatment “with (DOC + DTT) led to further losses of lipid material at the same time as strong swelling took place. As compared to the treatment with DTT alone, the additional loss of lipids occurred mainly from the (sterol glycoside + cerebroside + digalactosyl diglyceride –fraction) and from the solfolipid, with some losses also from the (pigments + neutral), phosphatidyl choline and phosphatidyl glycerol fractions.The results are in agreement with our earlier data, which also show that lipid fractionation is important for the revealing of (Na+ 4– K+)–stimulated ATPase activity, possibly because of the negative electric charge of the sulfolipid, which is characteristic for the induced preparations and which may be connected with the specific site of stimulation by the cations.

The relationship between fatty acid structure and the positional distribution of esterified fatty acids in phosphatidyl glycerol from Mycoplasma laidlawii B

1. 1. The distribution of a number of fatty acids between the 1- and 2-positions of phosphatidyl glycerol from Mycoplasma laidlawii B has been investigated. The fatty acid composition of the phosphatidyl glycerol was systematically altered so that the positional distribution values determined here are accurate reflections of the relative positional affinities of the individual fatty acids examined. 2. 2. The positional distribution of any given fatty acid constituent was independent of the amount of that acid in the phosphatidyl glycerol, provided that the fatty acid in question was not present in sufficient quantity to saturate the preferred position. 3. 3. Within any single class of fatty acids, the positional specificity was markedly dependent on the chain length of the fatty acid. The smaller the total number of carbon atoms, the lesser was the affinity for the 1-position. 4. 4. Positional distribution was also dependent on the structural characteristics of the fatty acids. The following is the order of the fatty acid classes arranged according to a decreasing affinity for the 1-position: straight-chain saturated > branched-chain saturated > trans-monounsaturated > cis-monounsaturated > cyclopropane > cis-diunsaturated.

The occurrence of delta 3-trans-hexadecenoic acid in phosphatidyl glycerol from spinach leaves.

Der Gehalt anΔ 3-trans-Hexadecensäure im Phosphatidylglycerol aus grünen Spinatblättern (Spinacea oleracea) erweist sich als auffallend hoch. Die enzymatische Hydrolyse zeigt die C16-Monoensäure mit derβ-Stelle des Phosphatids verknüpft.