Functional Roles of Non-membrane Lipids in Bacterial Signaling

2019 ◽  
pp. 273-289
Author(s):  
María J. Soto ◽  
N. Calatrava-Morales ◽  
Isabel M. López-Lara
Keyword(s):  
Membrane Lipids ◽  
Functional Roles ◽  
Bacterial Signaling

Functional Roles of Non-membrane Lipids in Bacterial Signaling

2017 ◽  
pp. 1-17 ◽  
Author(s):  
M. J. Soto ◽  
N. Calatrava-Morales ◽  
I. M. López-Lara
Keyword(s):  
Membrane Lipids ◽  
Functional Roles ◽  
Bacterial Signaling

Functional Roles of Non-membrane Lipids in Bacterial Signaling

2016 ◽  
pp. 1-17
Author(s):  
M. J. Soto ◽  
N. Calatrava-Morales ◽  
I. M. López-Lara
Keyword(s):  
Membrane Lipids ◽  
Functional Roles ◽  
Bacterial Signaling

Microscopy of membrane lipids: how precisely can we define their distribution?

2015 ◽  
Vol 57 ◽  
pp. 81-91 ◽  
Author(s):  
Sho Takatori ◽  
Toyoshi Fujimoto
Keyword(s):  
Membrane Lipids ◽  
Freeze Fracture ◽  
Practical Method ◽  
Membrane Lipid ◽  
Electron Microscopic ◽  
Functional Roles ◽  
Lipid Dynamics ◽  
Lipid Species ◽  
Quick Freezing ◽  
The Moment

Membrane lipids form the basic framework of biological membranes by forming the lipid bilayer, but it is becoming increasingly clear that individual lipid species play different functional roles. However, in comparison with proteins, relatively little is known about how lipids are distributed in the membrane. Several microscopic methods are available to study membrane lipid dynamics in living cells, but defining the distribution of lipids at the submicrometre scale is difficult, because lipids diffuse quickly in the membrane and most lipids do not react with aldehydes that are commonly used as fixatives. Quick-freezing appears to be the only practical method by which to stop the lipid movement instantaneously and capture the molecular localization at the moment of interest. Electron microscopic methods, using cryosections, resin sections, and freeze-fracture replicas are used to visualize lipids in quick-frozen samples. The method that employs the freeze-fracture replica is unique in that it requires no chemical treatment and provides a two-dimensional view of the membrane.

scholarly journals Lipid rafts and neurodegeneration: structural and functional roles in physiologic aging and neurodegenerative diseases

2019 ◽  
Vol 61 (5) ◽  
pp. 636-654 ◽  
Author(s):  
Sara Grassi ◽  
Paola Giussani ◽  
Laura Mauri ◽  
Simona Prioni ◽  
Sandro Sonnino ◽  
...  
Keyword(s):  
Neurodegenerative Diseases ◽  
Lipid Rafts ◽  
Membrane Lipids ◽  
Membrane Lipid ◽  
Lysosomal Storage ◽  
Functional Roles ◽  
Composition And Structure ◽  
Liquid Ordered ◽  
High Enrichment ◽  
And Function

Lipid rafts are small, dynamic membrane areas characterized by the clustering of selected membrane lipids as the result of the spontaneous separation of glycolipids, sphingolipids, and cholesterol in a liquid-ordered phase. The exact dynamics underlying phase separation of membrane lipids in the complex biological membranes are still not fully understood. Nevertheless, alterations in the membrane lipid composition affect the lateral organization of molecules belonging to lipid rafts. Neural lipid rafts are found in brain cells, including neurons, astrocytes, and microglia, and are characterized by a high enrichment of specific lipids depending on the cell type. These lipid rafts seem to organize and determine the function of multiprotein complexes involved in several aspects of signal transduction, thus regulating the homeostasis of the brain. The progressive decline of brain performance along with physiological aging is at least in part associated with alterations in the composition and structure of neural lipid rafts. In addition, neurodegenerative conditions, such as lysosomal storage disorders, multiple sclerosis, and Parkinson’s, Huntington’s, and Alzheimer’s diseases, are frequently characterized by dysregulated lipid metabolism, which in turn affects the structure of lipid rafts. Several events underlying the pathogenesis of these diseases appear to depend on the altered composition of lipid rafts. Thus, the structure and function of lipid rafts play a central role in the pathogenesis of many common neurodegenerative diseases.

scholarly journals Cytosolic termini of the FurE transporter regulate endocytosis, pH-dependent gating and specificity

2019 ◽  
Author(s):  
Georgia F. Papadaki ◽  
George Lambrinidis ◽  
Andreas Zamanos ◽  
Emmanuel Mikros ◽  
George Diallinas
Keyword(s):  
Molecular Dynamics ◽  
Uric Acid ◽  
Membrane Lipids ◽  
Substrate Selection ◽  
Transport Activity ◽  
Functional Roles ◽  
Gating Mechanism ◽  
C And N ◽  
Ph Dependent ◽  
Substrate Specifities

AbstractFurE, a member of the NCS1 family, is anAspergillus nidulanstransporter specific for uracil, allantoin and uric acid. Recently we showed that C- or N-terminally truncated FurE versions are blocked for endocytosis and, surprisingly, show modified substrate specifities. Bifluorescence complementation assays and genetic analyses supported that the C- and N-termini interact dynamically and through this interaction regulate selective substrate translocation. Here we functionally dissect and delimit distinct motifs crucial for endocytosis, transport activity, substrate specificity and folding, in both cytosolic termini of FurE. Subsequently, we obtain novel genetic andin silicoevidence supporting that the molecular dynamics of specific N- and C-terminal regions affect allosterically the gating mechanism responsible for substrate selection, via pH-dependent interactions with other internal cytosolic loops and membrane lipids. Our work shows that elongated cytoplasmic termini, acquired through evolution mostly in eukaryotic transporters, provide novel specific functional roles.

scholarly journals Distinct functional roles for hopanoid composition in the chemical tolerance ofZymomonas mobilis

2018 ◽  
Author(s):  
Léa Brenac ◽  
Edward E.K. Baidoo ◽  
Jay D. Keasling ◽  
Itay Budin
Keyword(s):  
Group Composition ◽  
Membrane Lipids ◽  
Head Group ◽  
Polar Group ◽  
Measured Concentration ◽  
Growth And Survival ◽  
Functional Roles ◽  
Bacterial Membranes ◽  
Transposon Mutants

SummaryHopanoids are abundant membrane lipids found in diverse bacterial lineages, but their physiological roles are not well understood. The ethanol fermenterZymomonas mobilisfeatures the highest measured concentration of hopanoids, leading to the hypothesis that these lipids can protect against bacterial solvent toxicity. However, the lack of genetic tools for manipulating hopanoid compositionin vivohas limited their further functional analysis. Because of polyploidy (> 50 genome copies per cell), we found that disruptions of essential hopanoid biosynthesis (hpn) genes inZ. mobilisact as genetic knockdowns, reliably modulating the abundance of different hopanoid species. Using a set ofhpntransposon mutants, we demonstrate that both reduced hopanoid content and modified hopanoid head group composition mediate growth and survival in ethanol. In contrast, the amount of hopanoids, but not their polar group composition, contributes to fitness at low pH. Spectroscopic analysis of model membranes showed that hopanoids protect against several ethanol-driven phase transitions in membrane structure, including lipid interdigitation and bilayer dissolution. We propose that hopanoids act through a combination of hydrophobic and inter-lipid hydrogen bonding interactions to stabilize bacterial membranes against solvent stress.Graphical abstract

The organization of cell surface membrane domains

1989 ◽  
Vol 47 ◽  
pp. 804-805
Author(s):  
Michael Edidin
Keyword(s):  
Cell Surface ◽  
Membrane Lipids ◽  
Surface Membrane ◽  
Lateral Diffusion ◽  
Cell Types ◽  
Membrane Domains ◽  
Membrane Biology ◽  
Morphological Polarity ◽  
Discrete Domains ◽  
Membrane Components

Cell surface membranes are based on a fluid lipid bilayer and models of the membranes' organization have emphasised the possibilities for lateral motion of membrane lipids and proteins within the bilayer. Two recent trends in cell and membrane biology make us consider ways in which membrane organization works against its inherent fluidity, localizing both lipids and proteins into discrete domains. There is evidence for such domains, even in cells without obvious morphological polarity and organization [Table 1]. Cells that are morphologically polarised, for example epithelial cells, raise the issue of membrane domains in an accute form.The technique of fluorescence photobleaching and recovery, FPR, was developed to measure lateral diffusion of membrane components. It has also proven to be a powerful tool for the analysis of constraints to lateral mobility. FPR resolves several sorts of membrane domains, all on the micrometer scale, in several different cell types.

Melatonin reduces high levels of lipid peroxidation induced by potassium iodate in porcine thyroid

2019 ◽  
pp. 1-7 ◽  
Author(s):  
Paulina Iwan ◽  
Jan Stepniak ◽  
Malgorzata Karbownik-Lewinska
Keyword(s):  
Lipid Peroxidation ◽  
Oxidative Damage ◽  
Membrane Lipids ◽  
Chemical Properties ◽  
Iodine Concentration ◽  
Free Radical Scavenger ◽  
Radical Scavenger ◽  
Protective Effects ◽  
Potassium Iodate ◽  
Hormone Synthesis

Abstract. Iodine is essential for thyroid hormone synthesis. Under normal iodine supply, calculated physiological iodine concentration in the thyroid is approx. 9 mM. Either potassium iodide (KI) or potassium iodate (KIO3) are used in iodine prophylaxis. KI is confirmed as absolutely safe. KIO3 possesses chemical properties suggesting its potential toxicity. Melatonin (N-acetyl-5-methoxytryptamine) is an effective antioxidant and free radical scavenger. Study aims: to evaluate potential protective effects of melatonin against oxidative damage to membrane lipids (lipid peroxidation, LPO) induced by KI or KIO3 in porcine thyroid. Homogenates of twenty four (24) thyroids were incubated in presence of either KI or KIO3 without/with melatonin (5 mM). As melatonin was not effective against KI-induced LPO, in the next step only KIO3 was used. Homogenates were incubated in presence of KIO3 (200; 100; 50; 25; 20; 15; 10; 7.5; 5.0; 2.5; 1.25 mM) without/with melatonin or 17ß-estradiol. Five experiments were performed with different concentrations of melatonin (5.0; 2.5; 1.25; 1.0; 0.625 mM) and one with 17ß-estradiol (1.0 mM). Malondialdehyde + 4-hydroxyalkenals (MDA + 4-HDA) concentration (LPO index) was measured spectrophotometrically. KIO3 increased LPO with the strongest damaging effect (MDA + 4-HDA level: ≈1.28 nmol/mg protein, p < 0.05) revealed at concentrations of around 15 mM, thus corresponding to physiological iodine concentrations in the thyroid. Melatonin reduced LPO (MDA + 4-HDA levels: from ≈0.97 to ≈0,76 and from ≈0,64 to ≈0,49 nmol/mg protein, p < 0.05) induced by KIO3 at concentrations of 10 mM or 7.5 mM. Conclusion: Melatonin can reduce very strong oxidative damage to membrane lipids caused by KIO3 used in doses resulting in physiological iodine concentrations in the thyroid.

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