Arginine-lysine positional swap of the LL-37 peptides reveals evolutional advantages of the native sequence and leads to bacterial probes

Antimicrobial peptides are essential components of the innate immune system of multicellular organisms. Although cationic and hydrophobic amino acids are known determinants of these amphipathic molecules for bacterial killing, it is not clear how lysine-arginine (K-R) positional swaps influence peptide structure and activity. This study addresses this question by investigating two groups of peptides (GF-17 and 17BIPHE2) derived from human cathelicidin LL-37. K-R positional swap showed little effect on minimal inhibitory concentrations of the peptides. However, there are clear differences in bacterial killing kinetics. The membrane permeation patterns vary with peptide and bacterial types, but not changes in fluorescent dyes, salts or pH. In general, the original peptide is more efficient in bacterial killing, but less toxic to human cells, than the K-R swapped peptides, revealing the evolutionary significance of the native sequence for host defense. The characteristic membrane permeation patterns for different bacteria suggest a possible application of these K-R positional-swapped peptides as molecular probes for the type of bacteria. Such differences are related to bacterial membrane compositions: minimal for Gram-positive Staphylococcus aureus with essentially all anionic lipids (cardiolipin and phosphatidylglycerol), but evident for Gram-negative Klebsiella pneumoniae, Pseudomonas aeruginosa and Escherichia coli with a mixture of phosphatidylethanolamine and phosphatidylglycerol. Biophysical characterization found similar structures and binding affinities for these peptides in vesicle systems mimicking E. coli and S. aureus. It seems that interfacial arginines of GF-17 are preferred over lysines in bacterial membrane permeation. Our study sheds new light on the design of cationic amphipathic peptides.

Comprehensive analysis of phospholipids and glycolipids in the opportunistic pathogen Enterococcus faecalis

Enterococcus faecalis is a Gram-positive, opportunistic, pathogenic bacterium that causes a significant number of antibiotic-resistant infections in hospitalized patients. The development of antibiotic resistance in hospital-associated pathogens is a formidable public health threat. In E. faecalis and other Gram-positive pathogens, correlations exist between lipid composition and antibiotic resistance. Resistance to the last-resort antibiotic daptomycin is accompanied by a decrease in phosphatidylglycerol (PG) levels, whereas multiple peptide resistance factor (MprF) converts anionic PG into cationic lysyl-PG via a trans-esterification reaction, providing resistance to cationic antimicrobial peptides. Unlike previous studies that relied on thin layer chromatography and spectrophotometry, we have performed liquid chromatography-tandem mass spectrometry (LC-MS/MS) directly on lipids extracted from E. faecalis, and quantified the phospholipids through multiple reaction monitoring (MRM). In the daptomycin-sensitive E. faecalis strain OG1RF, we have identified 17 PGs, 8 lysyl-PGs (LPGs), 23 cardiolipins (CL), 3 glycerophospho-diglucosyl-diacylglycerols (GPDGDAG), 5 diglucosyl-diacylglycerols (DGDAG), 3 diacylglycerols (DAGs), and 4 triacylglycerols (TAGs). We have quantified PG and shown that PG levels vary during growth of E. faecalis in vitro. We also show that two daptomycin-resistant (DapR) strains of E. faecalis have substantially lower levels of PG and LPG levels. Since LPG levels in these strains are lower, daptomycin resistance is likely due to the reduction in PG. This lipidome map is the first comprehensive analysis of membrane phospholipids and glycolipids in the important human pathogen E. faecalis, for which antimicrobial resistance and altered lipid homeostasis have been intimately linked.

The cellular lipids of Romboutsia

We have examined the lipids of three isolates, Romboutsia lituseburensis, Romboutsia ilealis, and Romboutsia sp. strain FRIFI, of the newly described genus Romboutsia by two-dimensional thin-layer chromatography (2D-TLC) and by liquid chromatography/mass spectrometry (LC/MS). We have found three phospholipids, phosphatidylglycerol (PG), cardiolipin and phosphatidic acid in all three species. A fourth phospholipid, lysyl-PG, was found in R. lituseburensis and strain FRIFI. Polyprenyl-phosphates were identified in the lipid extracts of all three species. Three glycolipids, mono-, di- and tri-hexosyldiacylglycerol, were common to all three species. An additional glycolipid, tetrahexosyl-diacylglycerol was identified in strain FRIFI. Acylated trihexosyldiacylglycerol and acyl-tetrahexosydiacylglycerol were also found in R. ilealis and strain FRIFI. Remarkably, no alk-1-enyl ether lipids (plasmalogens) were present in Romboutsia as distinct from bacteria of the related genus Clostridium in which these ether lipids are common. We have compared the lipidome of Romboutsia with that recently described for Clostridium difficile, which has plasmalogens, no lysyl-PG, and no tetrahexosyl-diacylglycerol. According to 16S rRNA gene sequencing, Romboutsia spp. and C. difficile are closely related (>95% sequence identity).

Grazing incidence diffraction studies of the interactions between ursane-type antimicrobial triterpenes and bacterial anionic phospholipids

α-Amyrin (AMalf) and ursolic acid (Urs) are ursane-type pentacyclic triterpenes which exhibit wide spectrum of antibacterial activity. These surface active compounds can be incorporated into bacterial membranes and alter their structure and function; however, the exact mechanism of their action still needs to be elucidated. Thus, we decided to study the interactions of these terpenes with specific anionic phospholipids:cardiolipins and phosphatidylglycerols extracted from Escherichia coli in the model environment of Langmuir monolayers. To characterize the ordering of the terpene molecules in one-component films as well as to study their interactions with the bacterial phospholipids in binary monolayers we applied grazing incidence X-ray diffraction (GIXD). It turned out that amyrins and ursolic acid molecules form crystalline hexagonal phases in Langmuir monolayers, in which the molecules are oriented uprightly. Regarding the mixtures, it was found that in the monolayers with Urs crystalline domains are present till moderate or even low Urs proportion. In contrast, in the mixtures with AMalf crystalline domains were observed only at the highest terpene concentration. In the interpretation of our results we underlined the significance of the interactions between the cyclopropane ring present in the hydrophobic part of the bacterial phospholipids and the terminal ring of the terpene structure. We proposed that the significant differences between the systems with AMalf and Urs are connected with the formation of hydrogen bonds between the Urs hydrophobic moieties. It can be inferred from the results that Urs is a more membrane-active agent than AMalf.

Studies of the interactions of ursane-type bioactive terpenes with the model of Escherichia coli inner membrane-Langmuir monolayer approach

Pentacyclic triterpenes (PT), ursolic acid (Urs), and α-amyrin (AMalf) are natural products exhibiting broad spectrum of antibacterial activity. These compounds are membrane-active and can disorder bacterial membranes when incorporated; however, the exact mechanism of their membrane activity is unknown. In our studies, we applied Langmuir monolayer technique supported by Brewster angle microscopy to model the interactions of the selected PT with the lipid matrix of E. coli inner membrane. As the model membrane, we applied mixtures (75/25 mole/.mole %) of the representative Escherichia coli phosphatidylethanolamine (POPE), with the cardiolipin (ECCL) or phosphatidylglycerol (ECPG) extracted from the E. coli inner membrane. On the basis of the recorded isotherms, we performed thermodynamic analysis and calculated free energy of mixing ΔGexc. It turned out that the phospholipids forming the inner membrane of E. coli are ideally miscible, whereas in binary systems composed of PT and POPE, negative deviations from ideality indicating attractive interactions between the investigated PT and POPE molecules were observed. On the other hand, in ternary systems composed of PT, POPE and one of the E. coli anionic phospholipids large positive changes in ΔGexc were observed. Thus, both PT exhibit disorganizing effect on the model E. coli membrane. It was also proved that at low terpene proportion, AMalf can be more active than Urs. However, at higher proportion Urs incorporation can lead to the disintegration of cardiolipin-rich domains present in bacterial membrane.

Polar lipids from the marine macroalga Palmaria palmata inhibit lipopolysaccharide-induced nitric oxide production in RAW264.7 macrophage cells

The EtOAc soluble fraction of a MeOH/CHCl3 extract of Palmaria palmata showed strong nitric oxide (NO) inhibitory activity against lipopolysaccharide (LPS)-induced NO production in murine RAW264.7 cells. NO inhibition-guided isolation led to identification of three new polar lipids including a sulfoquinovosyl diacylglycerol (SQDG) (2S)-1-O-eicosapentaenoyl-2-O-myristoyl-3-O-(6-sulfo-α-D-quinovopyranosyl)-glycerol (1) and two phosphatidylglycerols, 1-O-eicosapentaenoyl-2-O-trans-3-hexadecenoyl-3-phospho-(1'-glycerol)-glycerol (3) and 1-O-eicosapentaenoyl-2-O-palmitoyl-3-phospho-(1'-glycerol)-glycerol (4) from the EtOAc fraction. Seven known lipids were also isolated including a SQDG (2), a phospholipid (5) and five galactolipids (6-10). Structures of the isolated lipids were elucidated by spectral analyses. The isolated SQDGs, phosphatidylglycerols and phospholipid possessed strong and dose-dependent NO inhibitory activity compared to N(G)-methyl-L-arginine acetate salt (L-NMMA), a well-known NO inhibitor used as a positive control. Further study suggested that these polar lipids suppressed NO production through down-regulation of inducible nitric oxide synthase (iNOS).

Separation of cis-trans phospholipid isomers using reversed phase LC with high resolution MS detection

The increased presence of synthetic trans fatty acids into western diets has been shown to have deleterious effects on physiology and raising an individual's risk of developing metabolic disease, cardiovascular disease, and stroke. The importance of these fatty acids for health and the diversity of their (patho) physiological effects suggest that not only should the free trans fatty acids be studied but also monitoring the presence of these fats into the side chains of biological lipids, such as glycerophospholipids, is also essential. We developed a high resolution LC-MS method that quantitatively monitors the major lipid classes found in biospecimens in an efficient, sensitive, and robust manner while also characterizing individual lipid side chains through the use of high energy collisional dissociation (HCD) fragmentation and chromatographic alignment. We herein show how this previously described reversed phase method can baseline separate the cis-trans isomers of phosphatidylglycerol and phosphatidylcholine (PC) with two 18:1 side chains, in both positive and negative mode, as neat solutions and when spiked into a biological matrix. Endogenous PC (18:1/18:1)-cis and PC (18:1/18:1)-trans isomers were examined in mitochondrial and serum profiling studies, where rats were fed diets enriched in either trans 18:1 fatty acids or cis 18:1 fatty acids. In this study, we determined the cis:trans isomer ratios of PC (18:1/18:1) and related this ratio to dietary composition. This generalized LC-MS method enables the monitoring of trans fats in biological lipids in the context of a nontargeted method, allowing for relative quantitation and enhanced identification of unknown lipids in complex matrixes.

Functional analysis of a lipid galactosyltransferase synthesizing the major envelope lipid in the Lyme disease spirochete Borrelia burgdorferi

One of the major lipids in the membranes of Borrelia burgdorferi is monogalactosyl diacylglycerol (MGalDAG), a glycolipid recently shown to carry antigenic potency. Herein, it is shown that the gene mgs (TIGR designation bb0454) of B. burgdorferi encodes for the protein bbMGS that, when expressed in Escherichia coli, catalyzes the glycosylation of 1,2-diacylglycerol with specificity for the donor substrate UDP-Gal yielding MGalDAG. Related lipid enzymes were found in many Gram-positive bacteria. The presence of this galactosyltransferase activity and synthesis of a cholesteryl galactoside by another enzyme were verified in B. burgdorferi cell extract. Besides MGalDAG, phosphatidylcholine, phosphatidylglycerol, and cholesterol were also found as major lipids in the cell envelope. The high isoelectric point of bbMGS and clustered basic residues in its amino acid sequence suggest that the enzyme interacts with acidic lipids in the plasma membrane, in agreement with strong enzymatic activation of bbMGS by phosphatidylglycerol. The membrane packing and immunological properties of MGalDAG are likely to be of great importance in vivo.

Diacylglycerolipids isolated from a thermophile cyanobacterium from the Euganean hot springs

The Phormidium sp. ETS-05 thermophile blue-green alga is one of the most typical and widespread species of cyanobacteria of the thermal muds of the Euganean hot springs, the therapeutic properties of which have been known since ancient times. The polar diacylglycerolipids of this cyanobacterium consists of monogalactosyldiacylglycerol, digalactosyldiacylglycerol, sulfoquinovosyldiacylglycerol and phosphatidylglycerol. We have isolated and purified these four diacylglycerolipids from ETS-05, and then analysed them for their quantitative and structural features and fatty acid contents. The monogalactosyldiacylglycerol and digalactosyldiacylglycerol show a marked presence of polyunsaturated fatty acids, of which C18 : 4 is the most common. We propose that these glycoglycerolipids can be used as markers for monitoring the thermal mud colonisation process.

Molecular species of phosphatidylethanolamine from continuous cultures of Saccharomyces pastorianus syn. carlsbergensis strains

Saccharomyces pastorianus syn. carlsbergensis strain 34/70 is well known to be the most used strain for lager beer production. The difference between this strain and very closely related strain 34/78 is the latter's greater flocculating character. This single physiological trait can cause technical difficulties in beer production. The aim of this study was to determine whether lipid analysis by a combination of thin layer chromatography (TLC) with electrospray ionization mass spectrometry (ESI-MS) could be used as a strain-typing technique in order to distinguish S. pastorianus syn. carlsbergensis strain 34/70 from strain 34/78. Both strains (34/70 and 34/78) were harvested after continuous culture under standard conditions. Polar lipids were then extracted from lyophilized cultures and analysed by TLC in order to separate phospholipid families. Phosphatidylethanolamine (PE) was extracted and investigated using ESI-MS, to gain further information on individual molecular species. Using TLC analysis, lipids were separated corresponding to standards for PE, phosphatidylcholine (PC), phosphatidylglycerol (PG), cardiolipin (CL), phosphatidylserine (PS), phosphatidylinositol (PI), phosphatidic acid (PA) and sphingomyelin (SM). ESI-MS of the PE band, separated by TLC, showed that electrospray mass spectra were highly reproducible for repeat cultures. Novel findings were that both brewing strains displayed major phospholipid peaks with m/z 714, PE (34 : 2) m/z 742, PE (36 : 2) and m/z 758, PE (37 : 1). However, strain 34/78 had additional peaks of m/z 700, PE (33 : 2) and m/z 728, PE (35 : 2). Strain 34/70 had an extra peak with m/z 686 PE (32 : 2). We conclude that combined TLC/ESI-MS can distinguish between S. pastorianus syn. carlsbergensis 34/70 and 34/78 and may be a useful typing technique for differentiation of closely related yeast strains. This novel approach may aid quality assurance and could be suitable for yeast collections and larger industrial companies.

Asymmetric in vitro synthesis of diastereomeric phosphatidylglycerols from phosphatidylcholine and glycerol by bacterial phospholipase D

Using chiral-phase HPLC, we determined the stereochemical configuration of the phosphatidylglycerols (PtdGro) synthesized in vitro from 1,2-diacyl-sn-glycero-3-phosphocholine (PtdCho, R configuration) or 1,2-diacyl-sn-glycero-3-phosphoethanolamine (PtdEtn, R configuration) and glycerol by transphosphatidylation with bacterial phospholipase D (PLD). The results obtained with PLD preparations from three Streptomyces strains (S. septatus TH-2, S. halstedii K5, and S. halstedii subsp. scabies K6) and one Actinomadura species were compared with those obtained using cabbage and peanut PLD. The reaction was carried out at 30 degrees C in a biphasic system consisting of diethyl ether and acetate buffer. The resulting PtdGro were then converted into bis(3,5-dinitrophenylurethane) derivatives, which were separated on an (R)-1-(1-naphthyl)ethylamine polymer. In contrast to the cabbage and peanut PLD, which gave equimolar mixtures of the R,S and R,R diastereomers, as previously established, the bacterial PLD yielded diastereomixtures of 30-40% 1,2-diacyl-sn-glycero-3-phospho-1'-sn-glycerol (R,S configuration) and 60-70% 1,2-diacyl-sn-glycero-3-phospho-3'-sn-glycerol (R,R configuration). The highest disproportionation was found for the Streptomyces K6 species. The present study demonstrates that bacterial PLD-catalyzed transphosphatidylation proceeds to a considerable extent stereoselectively to produce PtdGro from PtdCho or PtdEtn and prochiral glycerol, indicating a preference for the sn-3' position of the glycerol molecule.

Effect of temperature on the stereoselectivity of phospholipase D toward glycerol in the transphosphatidylation of phosphatidylcholine to phosphatidylglycerol

In this study, the effect of temperature on the stereoselectivity of phospholipase D (PLD) toward the two primary hydroxyl groups of glycerol in the transphosphatidylation reaction of phosphatidylcholine to phosphatidylglycerol (PtdGro) was investigated. For this purpose, PLD from bacteria (Streptomyces septatus TH-2, S. halstedii subsp. scabies K6, and Actinomadura sp.) and cabbage were tested. At the reaction temperatures employed (0-60 degrees C), the proportions of the two PtdGro diastereomers, namely, 1,2-dioleoyl-sn-glycero-3-phospho-3'-sn-glycerol (R,R configuration) and 1 ,2-dioleoyl-sn-glycero-3-phospho-1'-sn-glycerol (R,S configuration), which were produced with PLD from Streptomyces TH-2 and Actinomadura sp., changed gradually from 50% R,R and 50% R,S at 50-60 degrees C to 70% R,R and 30% R,S at 0 degrees C. These alterations suggested that the stereoselectivity of the bacterial PLD toward the two primary hydroxyl groups of prochiral glycerol was significantly influenced by reaction temperature. PLD from Streptomyces K6 showed relatively little effect of temperature on stereoselectivity, giving 65-69% R,R in the temperature range of 60-10 degrees C examined. The plots of In ([R,R]/[R,S]) vs. 1/T gave good linear fits for these three bacterial PLD. No temperature effect was observed for cabbage PLD, which gave an almost equimolar mixture of the R,R and R,S diastereomers in the range from 0 to 40 degrees C. The temperature-dependent change in enantiomeric selectivity of the bacterial PLD promises potentially profitable commercial exploitation.

Phospholipids of Clostridium perfringens: a reexamination

We have identified phosphatidylethanolamine as one of the major phospholipids of Clostridium perfringens by two dimensional thin layer chromatography of the intact lipids and of their deacylation products and by liquid chromatography followed by mass spectrometry of the intact neutral phospholipid fraction. The principal fatty acids of phosphatidylethanolamine are myristic acid (14:0), lauric acid (12:0), and palmitic acid (16:0) and the major molecular species are 14:0,14:0 (26.3%); 12:0,14:0 (19.0%); 14:0,16:0 (22.4%) and 16:0,16:0 (17.6%). A similar distribution of molecular species was found in the other major phospholipid, O-alanyl phosphatidylglycerol.

Liposome adjuvants prepared from the total polar lipids of Haloferax volcanii, Planococcus spp. and Bacillus firmus differ in ability to elicit and sustain immune responses

Immune stimulating activity was compared for lipid vesicles consisting of the total polar lipids of an archaeon Haloferax volcanii, and the eubacteria Planococcus spp. and Bacillus firmus. Each total polar lipid extract readily formed liposomes of similar size, within which the protein antigen ovalbumin was entrapped, with comparable loading and internalization. Subcutaneous immunization of mice resulted in anti-ovalbumin antibody titers for all adjuvants, with memory recall responses that were significantly greater with the archaeal lipid (H. volcanii versus Planococcus). More striking, induction of cytotoxic T cell activity against the entrapped antigen, measured 10 days following a single vaccination (primary response) rapidly declined by week 7 (secondary response after injections on days 0 and 21) in mice immunized with Planococcus spp. liposomes, but was sustained in mice immunized with H. volcanii archaeosomes. Surprisingly, antigen free-Planococcus liposomes evoked potent non-specific inflammatory cytokine production (IL-12 and IL-6) by dendritic cells whereas archaeal H. volcanii vesicles evoked little inflammatory cytokines. This suggested that overt inflammatory response might not necessarily aid sustenance of immunity. B. firmus liposomes consisted of phosphatidylglycerol, phosphatidylethanolamine and cardiolipin and was an ineffective CTL adjuvant, even for initiating a primary response. Considering that the polar lipids of H. volcanii and Planococcus spp. both consist of the same lipid classes (sulfoglycolipids, phosphoglycerols, and cardiolipins), the unique ability of archaeosomes to maintain antigen-specific T cell immunity may be attributable to a property of the archaeal 2,3-diphytanylglycerol lipid core.

A study of moss (Marchantia polymorpha) thylakoid membrane lipids in monolayers

Monolayers of seven fractions of natural lipids (phosphatidyl inositol, sulfoquinovosyl diacylglycerol, phosphatidylcholine, digalactosyl diacylglycerol, phosphatidyl glycerol, phosphatidylethanolamine, monogalactosyl diacylglycerol), isolated from the photoautotrophic cell culture of the moss Marchantia polymorpha grown under normal and light-stress conditions, have been prepared for the first time. We have shown that the high-intensity light affects the area occupied by the lipid molecule. In the case of digalactosyl diacylglycerol and phosphatidyl glycerol fractions, after the light stress the area significantly increased from 0.50 to 0.80 nm2 and from 0.47 to 0.63 nm2, respectively, and in the case of the sulfoquinovosyl diacylglycerol fraction, the area decreased from 0.40 to 0.32 nm2. These results are in agreement with our previous data on the redistribution of the double bonds in the aliphatic chains of these lipids and can be used to characterize the state of the lipid bilayer of the thylakoid membranes.

Reassessment of stereochemical configuration of natural phosphatidylglycerols by chiral-phase high-performance liquid chromatography and electrospray mass spectrometry

Using chiral-phase high-performance liquid chromatography (HPLC) and electrospray ionization-mass spectrometry (ESI/MS), we have redetermined the stereochemical configuration of some natural and synthetic phosphatidylglycerols (PG). For this purpose, the synthetic and natural PG were converted to their bis-3,5-dinitrophenylurethanes (DNPU), which were separated by HPLC using two columns having chiral phases of opposite configuration, (R)-(+)- and (S)-(-)-1-(1-naphthyl)ethylamine polymers. The molecular species were identified by on-line negative-ion ESI/MS. Absolute configurations of the resolved peaks were assigned by comparison with the elution order of the corresponding 1(3)-monoacyl-sn-glycerol enantiomers as bis-DNPU derivatives on the same column. The results clearly showed that the PG from cabbage leaf lipids and soybean phospholipids consisted of single R,S isomers (1,2-diacyl-sn-glycero-3-phospho-1'-sn-glycerols), despite the presence of nonstereospecific phospholipase D in the tissues. On the other hand, the PG derived from egg yolk phosphatidylcholine and glycerol by transphosphatidylation with cabbage phospholipase D was a mixture of 45% R,S isomers (1, 2-diacyl-sn-glycero-3-phospho-1'-sn-glycerols) and 55% R,R isomers (1,2-diacyl-sn-glycero-3-phospho-3'-sn-glycerols). The PG from Escherichia coli lipids was a mixture of 89% R,S and 11% R,R isomers. The present study demonstrates that chiral-phase HPLC and negative-ion ESI/MS provide direct and unambiguous information about the configuration, identity, and quantity of molecular species in natural and synthetic PG.

Studies on thermophile products. X. Further biological properties of isofatty acid-containing phosphatidylglycerol that enhances the induction of suppressor T cells

Isofatty acid-containing phosphatidylglycerol (Fr. 7-C), isolated from Bacillus stearothermophilus UBT8038, enhances the induction of concanavalin A (Con A)-activated suppressor T (Ts) cells in a dose dependent manner (0.01-1 microgram/ml). Its further biological properties on mouse mixed lymphocyte reaction (MLR) has been demonstrated. Fr. 7-C (0.01-1 microgram/ml) suppressed the MLR at 4 d in a dose-dependent manner when added at the start of splenocyte cultivation. Moreover, Fr. 7-C was effective in preventing the generation of cytotoxic T lymphocytes after the MLR. On the other hand, this fraction significantly enhanced the induction of Ts cells in the MLR carried out in any of the antigen-specific, antigen-nonspecific and major histocompatibility complex antigen-nonrestricted fashions. Fr. 7-C increased prostaglandin E2 (PGE2) release approximately 2-fold in the culture supernatant of Con A-activated splenocytes, and PGE2 release decreased dose-dependently when cultured with indomethacin. The inhibitory effect by Fr. 7-C on the MLR was abrogated by the addition of indomethacin. The enhancement by Fr. 7-C on Ts cell induction was blocked by indomethacin in a dose dependent manner. These results strongly suggest that Fr. 7-C suppresses the MLR via the enhancement of antigen-nonspecific Ts cell induction mediated at least partly by PGE2.

Studies on thermophile products. IX. Isofatty acid-containing phosphatidylglycerol that enhances the induction of concanavalin A-activated suppressor T cells

A new enhancer of the induction of concanavalin A (Con A)-activated suppressor T (Ts) cells has been demonstrated in the ethanolysate of Bacillus stearothermophilus UBT8038. It was purified by successive silica gel column chromatographies and identified as phosphatidylglycerol with C14:0-C18:0 isofatty acids (Fr. 7-C). Mouse splenocytes activated with Con A and Fr. 7-C (0.01-1 microgram/ml) in vitro significantly suppressed the proliferative response of syngenic splenocytes by mitogen stimulation in a dose-dependent manner, compared to those stimulated by Con A alone. The immunosuppressive response enhanced by Fr. 7-C disappeared when the cell populations of Thy-1.2 or CD8 positive lymphocytes were depleted. The result strongly suggests that Fr. 7-C is an immunosuppressive substance which enhances the induction of Con A-activated CD8 positive Ts cells.

On the revised structure of the major phospholipid of Halobacterium salinarium

Recent fast atom bombardment-mass spectrometry (FABMS) studies (Tsujimoto, K., Yorimitsu, S., Takahashi, T. and Ohashi, M. (1989) J. Chem. Commun. 668-670; Frederickson, H.L., De Leeuw, J.W., Tas, A.C., Van der Greef, J., LaVos, G.F. and Boon, J.J. (1989) Biomed. Environ. Mass. Spectrom. 18, 96-105; Kloppel, K.D. and Fredrickson, H.L. (1991) J. Chromatogr. 562, 369-376) have indicated that the structure of the major phospholipid of Halobacterium salinarium (formerly Halobacterium cutirubrum) is not 2,3-diphytanyl-sn-glycerol-1-phospho-3'-sn-glycerol-1'- phosphate (PGP), but the monomethylated derivative, 2,3-diphytanyl-sn-glycerol-1-phospho-3'-sn-glycerol-1'-methylphosphate (PGP-Me). We have now confirmed the structure of the major phospholipid of extremely halophilic archaebacteria as being this methylated structure (PGP-Me) by 1H- and 13C-NMR, FABMS and TLC of the native phospholipid and its product of mild acid hydrolysis PGP. The methylated structure (PGP-Me), rather than PGP itself, is also the major phospholipid in species of other genera of extreme halophiles examined so far, such as, Haloferax, Haloarcula, Halococcus, Natronobacterium and Natronococcus.

Isolation of a phospholipid inhibitor of platelet activating factor-induced activity from perfused rat liver: identification as phosphatidylglycerol

An endogenous inhibitor of platelet activating factor action was isolated from perfused rat liver. It was purified by thin-layer chromatography and high-performance liquid chromatography and subjected to chemical modifications in order to identify its structure. On the basis of its fast atom bombardment-mass spectrum it was characterized as phosphatidylglycerol composed mainly of 16:0/18:1 and 16:0/20:2 fatty acyl chains ([M+H]+ at m/z 749 and 775, respectively) and very minor levels of 18:0/18:1 and 18:0/20:2. The purified compound exhibited inhibition on rabbit platelet aggregation induced by 5 x 10(-10) M platelet activating factor (PAF) at an EC50 value near 2.5 x 10(-6) M and on the serotonin secretion at an EC50 7 x 10(-6) M. Other phospholipids isolated from the liver preparations, such as phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, sphingomyelin, cardiolipin (diphosphatidylglycerol), and phosphatidic acid, exhibited no inhibitory activity in the concentration range from 1 x 10(-4) to 1 x 10(-7) M nor did they induce any aggregation, or lysis, of the platelets. Of importance, phosphatidylglycerol could inhibit thrombin- and ADP-induced aggregation of rabbit platelets. These results suggested a possible site of inhibition common to the signal transduction pathway of these agonists. Preliminary binding experiments showed a noncompetitive type of inhibition on PAF binding to intact rabbit platelets.

Biosynthesis and characterization of phosphatidylglycerophosphoglycerol, a possible intermediate in lipoteichoic acid biosynthesis in Streptococcus sanguis

A membrane enzyme preparation from Streptococcus sanguis was shown to convert sn-[14C]glycerol 3-phosphate and CDP-diacylglycerol (or deoxyCDP-diacylglycerol) into a series of progressively higher-molecular-weight [14C]oligophosphoglycerophospholipids in vitro. The first oligophosphoglycerophospholipid to accumulate (termed lipid-1) was purified to homogeneity; chemical analysis, gas-liquid chromatography and chemical degradation studies indicated the most likely structure to be phosphatidylglycerophosphoglycerol (PGpG). PGpG is formed directly from two molecules of phosphatidylglycerol (PG), one molecule of PG serving as a sn-glycerol 1-phosphate (pG) donor and the second serving as the pG acceptor, with co-production of diacylglycerol. These oligophosphoglycerophospholipids may be intermediates in the biosynthesis of lipoteichoic acids.

Interdigitated gel phase bilayers formed by unsaturated synthetic and bacterial glycerolipids in the presence of polymyxin B and glycerol

The ability of synthetic phosphoglycerolipids with a cis mono-unsaturated acyl chain in the 2-position and a saturated chain in the 1-position of glycerol to form interdigitated gel phase bilayers in the presence of amphipathic substances was monitored using a fatty acid spin label, 16-doxylstearic acid, and a phosphatidylglycerol spin label containing 16-doxylstearic acid. These spin labels become significantly more motionally restricted in an interdigitated gel phase bilayer than in a non-interdigitated gel phase bilayer. The results indicated that polymyxin B and polymyxin B nonapeptide caused interdigitation of 1-palmitoyl,2-oleoyl-phosphatidylglycerol (POPG) and glycerol caused interdigitation of 1-stearoyl,2-oleoyl-phosphatidylcholine (SOPC), similar to their effects on disaturated lipids. The fluidity gradient present in non-interdigitated gel phase bilayers was abolished. However, glycerol did not cause POPG to become interdigitated, in contrast to SOPC. We reported earlier that there is a kinetic barrier to interdigitation of saturated PG in the presence of glycerol, in contrast to saturated PC. This barrier is even greater for the unsaturated species of PG. Furthermore, these compounds lowered the gel to liquid-crystalline phase transition temperatures of the unsaturated lipids more than of saturated lipids suggesting that the interdigitated bilayer of the former may be less ordered or less stable than that of the latter. Since polymyxin B is an antibiotic we also examined its effect on a lipid extract from the Gram-negative bacteria Pseudomonas aeruginosa in order to assess whether interdigitation might be involved in its mechanism of bactericidal or bacteriostatic effect. Polymyxin B and polymyxin B nonapeptide also caused motional restriction of a small percentage (about 13% at -2 degrees C and 25% at -14 degrees C for polymyxin B) of the spin label in the lipid extract at low temperatures, where the lipid is in the gel phase, consistent with formation of a small domain of interdigitated bilayer lipid. However, the degree of immobilization was less than that in the interdigitated bilayers of the synthetic unsaturated lipids. This may be a result of the heterogeneous nature of the lipids in the extract. However, it cannot be ruled out that the motional restriction of the spin label in this extract may be caused by something other than interdigitation. Thus the results with the lipid extract are less conclusive of interdigitation than for the synthetic lipids. A motionally restricted population was not detectable at higher temperatures.(ABSTRACT TRUNCATED AT 400 WORDS)

Phospholipids co-isolated with rat surfactant protein C account for the apparent protein-enhanced uptake of liposomes into lung granular pneumocytes

Phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) were co-isolated with the low molecular weight rat surfactant-associated protein C (SP-C) of Mr approximately equal to 6,000. The contribution of these phospholipids to the incorporation of 3H-labeled phosphatidylcholine (PC) liposomes into rat alveolar type II cells stimulated by SP-C was examined. PG showed a concentration-dependent enhancement in the uptake of PC liposomes by the pneumocytes. PE alone had no effect but could inhibit the incorporation of liposomal PC stimulated by PG depending on the concentration of PG and the PG to PE ratio. SP-C augmented the cellular uptake of the PC liposomes only when the SP-C preparation had a protein to phospholipid ratio greater than 1 and a PG to PE ratio greater than 2. The results with the isolated SP-C could be reproduced using mixtures of PG and PE which reflected the phospholipid composition of the SP-C in the absence of SP-C protein. Thus, the ability of SP-C to stimulate liposomal PC uptake by rat type II cells could be accounted for by its phospholipid composition.

Lipid requirement of the branched-chain amino acid transport system of Streptococcus cremoris

The role of the membrane lipid composition on the transport protein of branched-chain amino acids of the homofermentative lactic acid bacterium Streptococcus cremoris has been investigated. The major membrane lipid species identified in S. cremoris were acidic phospholipids (phosphatidylglycerol and cardiolipin), glycolipids, and glycerophosphoglycolipids. Phosphatidylethanolamine (PE) was completely absent. Protonmotive force-driven and counterflow transport of leucine was assayed in fused membranes of S. cremoris membrane vesicles and liposomes composed of different lipids obtained by the freeze/thaw-sonication technique. High transport activities were observed with natural S. cremoris and Escherichia coli lipids, as well as with mixtures of phosphatidylcholine (PC) with PE or phosphatidylserine. High transport activities were also observed with mixtures of PC with monogalactosyl diglyceride, digalactosyl diglyceride, or a neutral glycolipid fraction isolated from S. cremoris. PC or mixtures of PC with phosphatidylglycerol, phosphatidic acid, or cardiolipin showed low activities. In mixtures of PC and methylated derivatives of PE, both counterflow and protonmotive force-driven transport activities decreased with increasing degree of methylation of PE. The decreased transport activity in membranes containing PC could be restored by refusion with PE-containing liposomes. These results demonstrate that both aminophospholipids and glycolipids can be activators of the leucine transport system from S. cremoris. It is proposed that aminophospholipids in Gram-negative bacteria and glycolipids in Gram-positive bacteria have similar functions with respect to solute transport.

Isolation of the acidic phospholipid phosphatidylglycerol from pulmonary surfactant by sorbent extraction chromatography

Aminopropyl solid-phase columns can be used for phospholipid fractionation. A method has been developed to elute the acidic phospholipid phosphatidylglycerol (PG) separately, and it is applicable to both standard (phospho)lipid mixtures and pulmonary surfactants. The simplicity, rapidity, and high recovery make this method of isolating PG superior to other chromatographic procedures.

A neutron diffraction study of the headgroup conformation of phosphatidylglycerol from Escherichia coli membranes

By using neutron diffraction, the headgroup conformation of purified phosphatidylglycerol from Escherichia coli membranes has been investigated. Measurements at 25 degrees C and 15% relative humidity on oriented multilayers of lipid selectively deuterated at the sn-3-position of the glycerol backbone and of the gamma-position of the glycerol headgroup show that the labels are at a mean distance of 23.0 A and 27.6 A from the centre of the hydrocarbon chain region. This suggests that the negatively charged headgroup is oriented at about 30 degrees to the membrane surface. The orientation of the phosphatidylglycerol headgroup makes the negatively charged phosphate group easily accessible to cations present in the adjacent water layer.

An improved preparation of phosphatidylglycerophosphate

Phosphatidylglycerophosphate is not normally accumulated in the reaction mixture. It was found that octyl-beta-D-glucopyranoside greatly stimulated the synthesis and inhibited the degradation of phosphatidylglycerophosphate. The phenomenon could be used for the preparation of phosphatidylglycerophosphate from CDPdiacylglycerol and the sn-glycero-3-phosphate with the crude membrane enzyme preparation. The optimal concentration of octyl-beta-D-glucopyranoside to be used for such a purpose was 24.5 mM.

High-performance liquid chromatographic determination of the lecithin/sphingomyelin ratio in amniotic fluid

A high-performance liquid chromatographic (HPLC) procedure has been developed for the separation of phospholipids commonly found in amniotic fluid. The chromatographic separation was achieved on a 25-cm column packed with LiChrosorb DIOL (10 mum). A 3-cm column packed with silica was fitted between the injector and the DIOL column to provide complete separation of lecithin (L) and sphingomyelin (S) from the remaining amniotic fluid phospholipids. The eluted phospholipids were quantitated employing an ultraviolet absorption detector set at 203 nm. The new HPLC separation described herein has improved the resolution and peak sharpness of L and S. Furthermore, phosphatidyl glycerol and phosphatidyl inositol were completely separated and quantitated. Amniotic fluid L/S ratios determined by this technique have been compared to those of an established thin-layer chromatographic procedure.

Acyl phosphatidylglycerol of Escherichia coli

Acyl phosphatidylglycerol, isolated from Escherichia coli, has been identified as 3-sn-phosphatidyl-1'-(3'-acyl)-sn-glycerol. The fatty acids of the diacylglycerol moiety of acyl phosphatidylglycerol resemble those of phosphatidylglycerol in composition. However, the monoacylglycerol moiety of this lipid contains more unsaturated fatty acids than the diacylglycerol part of this lipid or other phospholipids in E. coli. Furthermore, the fatty acids present in the monoacylglycerol moiety, were found to contain major amounts of an unsaturated acid identified as 7-tetradecenoic acid by combined gas-liquid chromatography-mass spectrometry. This acid was present only in low concentrations in most phospholipids of E. coli.

Estimation of phosphatidylglycerol in fluids containing pulmonary surfactant

A simple, direct and non-destructive method for quantitative separation of phosphatidylglycerol from other phospholipids in pulmonary washings is described. Total lipid extracts from dog lung washings and phosphatidylglycerol standard were spotted quantitatively on chromatoplates and separated by one-dimensional thin-layer chromatography in chloroform-methanol-water 65:25:4 (v/v/v). Quantification was performed with Rhodamine 6G and fluorometry. Washings from eleven dogs contained (mean +/- S.E.) 236 +/- 25 microgram phosphatidylglycerol per g of parenchymal wet lung tissue which accounted for 8.7% +/- 2.3 of the total phospholipids. The procedure is especially useful for quantification of phosphatidylglycerol in microgram amounts.

Secretory IgA is a component of rabbit lung surfactant

Secretory IgA is a major protein component of rabbit lung surfactant purified by NaBr density gradient centrifugation from endobronchial lavage and minced lung tissue. Secretory IgA was found in both surfactant and non-surfactant fractions obtained from endobronchial lung washings. By contrast in minced-lung washings, which are not contaminated with proteins from the upper respiratory tree, secretory IgA is prominent only in the surfactant fraction. These findings indicate that in rabbit lung secretory IgA is present in the alveoli and is intimately associated with the surfactant system.

An improved two dimensional thin-layer chromatography system for the separation of phosphatidylglycerol and its derivatives

A two dimensional thin-layer chromatography system has been devised for the improved separations of phosphatidylglycerol and its derivaties, cardiolipin and bis/monoacylglyceryl)phosphate, from the other phospholipid components of tissue total lipid extracts. The system employs silica gel G plates prepared with 0.4 M boric acid. Linear recovery of added phosphatidylglycerol was found, and phosphatidylglycerol did not cochromatograph with N, N-dimethylphosphatidylethanolamine in this system. The phospholipid class composition of various rat tissues and a Morris 7777 hepatoma has been determined and compared with values from the literature.