			Home About us Contact

Membrane Lipid Composition (membrane + lipid_composition)

Distribution by Scientific Domains

Life Sciences	60%

Selected Abstracts

Multifunctional host defense peptides: intracellular-targeting antimicrobial peptides

FEBS JOURNAL, Issue 22 2009
Pierre Nicolas
There is widespread acceptance that cationic antimicrobial peptides, apart from their membrane-permeabilizing/disrupting properties, also operate through interactions with intracellular targets, or disruption of key cellular processes. Examples of intracellular activity include inhibition of DNA and protein synthesis, inhibition of chaperone-assisted protein folding and enzymatic activity, and inhibition of cytoplasmic membrane septum formation and cell wall synthesis. The purpose of this minireview is to question some widely held views about intracellular-targeting antimicrobial peptides. In particular, I focus on the relative contributions of intracellular targeting and membrane disruption to the overall killing strategy of antimicrobial peptides, as well as on mechanisms whereby some peptides are able to translocate spontaneously across the plasma membrane. Currently, there are no more than three peptides that have been convincingly demonstrated to enter microbial cells without the involvement of stereospecific interactions with a receptor/docking molecule and, once in the cell, to interfere with cellular functions. From the limited data currently available, it seems unlikely that this property, which is isolated in particular peptide families, is also shared by the hundreds of naturally occurring antimicrobial peptides that differ in length, amino acid composition, sequence, hydrophobicity, amphipathicity, and membrane-bound conformation. Microbial cell entry and/or membrane damage associated with membrane phase/transient pore or long-lived transitions could be a feature common to intracellular-targeting antimicrobial peptides and mammalian cell-penetrating peptides that have an overrepresentation of one or two amino acids, i.e. Trp and Pro, His, or Arg. Differences in membrane lipid composition, as well as differential lipid recruitment by peptides, may provide a basis for microbial cell killing on one hand, and mammalian cell passage on the other. [source]

Absence of Gup1p in Saccharomyces cerevisiae results in defective cell wall composition, assembly, stability and morphology

FEMS YEAST RESEARCH, Issue 7 2006
Célia Ferreira
Abstract Saccharomyces cerevisiae Gup1p and its homologue Gup2p, members of the superfamily of membrane-bound O -acyl transferases, were previously associated with glycerol-mediated salt-stress recovery and glycerol symporter activity. Several other phenotypes suggested Gup1p involvement in processes connected with cell structure organization and biogenesis. The gup1, mutant is also thermosensitive and exhibits an altered plasma membrane lipid composition. The present work shows that the thermosensitivity is independent of glycerol production and retention. Furthermore, the mutant grows poorly on salt, ethanol and weak carboxylic acids, suggestive of a malfunctioning membrane potential. Additionally, gup1, is sensitive to cell wall-perturbing agents, such as Calcofluor white, Zymolyase, lyticase and sodium dodecyl sulphate and exhibits a sedimentation/aggregation phenotype. Quantitative analysis of cell wall components yielded increased contents of chitin and ,-1,3-glucans and lower amounts of mannoproteins. Consistently, scanning electron microscopy showed a strikingly rough surface morphology of the mutant cells. These results suggest that the gup1, is affected in cell wall assembly and stability, although the Slt2p/MAP kinase from the PKC pathway was phosphorylated during hypo-osmotic shock to a normal extent. Results emphasize the pleiotropic nature of gup1,, and are consistent with a role of Gulp1p in connection with several pathways for cell maintenance and construction/remodelling. [source]

Effects of modification of membrane lipid composition on Bacillus subtilis sporulation and spore properties

JOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2009
K.K. Griffiths
Abstract Aims:, To determine effects of inner membrane lipid composition on Bacillus subtilis sporulation and spore properties. Methods and Results:, The absence of genes encoding lipid biosynthetic enzymes had no effect on B. subtilis sporulation, although the expected lipids were absent from spores' inner membrane. The rate of spore germination with nutrients was decreased c. 50% with mutants that lacked the major cardiolipin (CL) synthase and another enzyme for synthesis of a major phospholipid. Spores lacking the minor CL synthase or an enzyme essential for glycolipid synthesis exhibited 50,150% increases in rates of dodecylamine germination, while spores lacking enzymes for phosphatidylethanolamine (PE), phosphatidylserine (PS) and lysylphosphatidylglycerol (l-PG) synthesis exhibited a 30,50% decrease. Spore sensitivity to H2O2 and tert-butylhydroperoxide was increased 30,60% in the absence of the major CL synthase, but these spores' sensitivity to NaOCl or OxoneÔ was unaffected. Spores of lipid synthesis mutants were less resistant to wet heat, with spores lacking enzymes for PE, PS or l-PG synthesis exhibiting a two to threefold decrease and spores of other strains exhibiting a four to 10-fold decrease. The decrease in spore wet heat resistance correlated with an increase in core water content. Conclusions:, Changing the lipid composition of the B. subtilis inner membrane did not affect sporulation, although modest effects on spore germination and wet heat and oxidizing agent sensitivity were observed, especially when multiple lipids were absent. The increases in rates of dodecylamine germination were likely due to increased ability of this compound to interact with the spore's inner membrane in the absence of some CL and glycolipids. The effects on spore wet heat sensitivity are likely indirect, because they were correlated with changes in core water content. Significance and Impact of the Study:, The results of this study provide insight into roles of inner membrane lipids in spore properties. [source]

Polyunsaturated Fatty Acid Regulation of Gene Expression

NUTRITION REVIEWS, Issue 9 2004
Harini Sampath B.Sc.
Polyunsaturated fatty acids (PUFAs), specifically the n-3 series, have been implicated in the prevention of various human diseases, including obesity, diabetes, coronary heart disease and stroke, and inflammatory and neurologic diseases. PUFAs function mainly by altering membrane lipid composition, cellular metabolism, signal transduction, and regulation of gene expression. PUFAs regulate the expression of genes in various tissues, including the liver, heart, adipose tissue, and brain. The role of transcription factors such as SREBP1c and nuclear receptors such as PPAR-,, HNF-4,, and LXR, in mediating the nuclear effects of PUFAs are addressed. [source]