• Journal of Microbiology and Biotechnology
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• v.29 no.1
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• pp.1-10
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• 2019

Gram-negative pathogens, such as Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii, pose a serious threat to public health worldwide, due to high rates of antibiotic resistance and the lack of development of novel antimicrobial agents targeting Gram-negative bacteria. The outer membrane (OM) of Gram-negative bacteria is a unique architecture that acts as a potent permeability barrier against toxic molecules, such as antibiotics. The OM is composed of phospholipids, lipopolysaccharide (LPS), outer membrane ${\beta}-barrel$ proteins (OMP), and lipoproteins. These components are synthesized in the cytoplasm or in the inner membrane, and are then selectively transported to the OM by the specific transport machines, including the Lol, BAM, and Lpt pathways. In this review, we summarize recent studies on the assembly systems of OM components and analyze studies for the development of inhibitors that target these systems. These analyses show that OM assembly machines have the potential to be a novel attractive drug target of Gram-negative bacteria.

• Applied Biological Chemistry
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• v.26 no.1
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• pp.58-64
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• 1983

The fatty acid composition of phospholipid from the leaves of rice plants grown at $28^{\circ}C$ and harvested at the 3-4 leaf stage was determined for 8 cultivars. Change among cultivars observed in the composition has been found to be correlative to the chilling susceptivity of the plants at the given leaf-stage. The chilling-resistant cultivars contain phospholipid with higher degree of unsaturation and larger relative proportion of unsaturated fatty acids than the chilling-sensitive ones. The indices for unsaturation of phospholipid from a cultic-ar are well in accordance with its resistance to cold damage. clearly demonstrating that the fluidity of biomembrane which is generally regarded as the prerequisite for a cell to maintain its membrane-related physiological activity at a low temperature is exclusively controlled by the fatty acid composition of phospholipid. Also identified were the components of phospholipid, which are phosphatidyl serine and phosphatidyl coline as major components and phosphatidyl inositol as minor component plus 3 phospholipids in trace proportion, from every cultivar at the early growth-stage.

• Proceedings of the Membrane Society of Korea Conference
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• 1999.07a
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• pp.100-101
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• 1999

• Molecules and Cells
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• v.41 no.1
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• pp.45-49
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• 2018

Autophagy is a lysosome-dependent degradation process that is essential for maintaining cellular homeostasis. In recent years, more studies have focused on the late stages of autophagy. Our group discovered and studied the terminal step of autophagy, namely autophagic lysosome reformation (ALR). ALR is the process that regenerates functional lysosomes from autolysosomes, thus maintaining lysosome homeostasis. ALR involves clathrin-mediated membrane budding from autolysosomes, elongation of membrane tubules along microtubules with the pulling force provided by the motor protein KIF5B, proto-lysosome scission by dynamin 2, and finally maturation of proto-lysosomes to functional lysosomes. In this review, we will summarize progress in unveiling the molecular mechanisms underlying ALR and its potential pathophysiological roles.

• KSBB Journal
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• v.7 no.4
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• pp.302-307
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• 1992

Protein phosphatase 2A was obtained from a cytosolic fraction of bovine brain homogenate. The phosphatase activity using phosphorylated histone Hl as substrate was suppressed in the presence of liposomes composed of dipalmitoylphosphatidylcholine(DPPC) or the mixture of phosphatidylserine and DPPC. The binding of protein phosphatase to liposome was indicated by the facts that the phosphatase activity of the supernatant of protein phosphatase/multilayer vesicle mixture was decreased with increasing amount of liposome, and that [$^{125}I$]-labeled protein phosphatase was coeluted with liposome. However, the affinity of the protein for phospholipid membrane was not so high. On the other hand, okadaic acid and liposome reduced the phosphatase activity synergistically, which means that okadaic acid binds neither to lipid membrane nor to the membrane-associated phosphatase, The inhibitory effect of liposome was, therefore, ascribed to association of the protein phosphatase 2A with the lipid bilayer membrane.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.4
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• pp.743-750
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• 1997

Direct measurement of the kinetics of free fatty acid transfer between phospholipid model membrane is technically limited by the rapid nature of the transfer process. Separation of membrane-bound fatty acid by centrifugation has shown that although the equilibrium distribution of free fatty acid is determined by this method, fatty acid transfer occurs too rapidly for accurate kinetic measurements. Recently fluorescence resonance energy transfer(FRET) assay has been developed to examine transfer of fatty acids between membranes. Donor membranes which has fluorescent fatty acid, anthroyloxy fatty acid(AOFA), is mixed with acceptor membranes which has non-interchangeable fluorescent quencher, nitrobenzo-xadiazol(NBD), using stopped flow apparatus. As the fluorescent fatty acids transfer from donor membrane to acceptor membrane, fluorescence intensity would be decreased and the rate and degree of fatty acid transfer can be analyzed. Fatty acid transfer between micelles is more complicated because of bile salt. Therefore in experiments with micelles, fluorescence self quenching assay is used. At high concentrations, a fluorophore tends to quench its own fluorescence causing a reduction in fluorescence intensity. Donor micelles contained self quenching concentrations of fluorophore and acceptor micelles had no fluorophore. Upon mixing of donor and acceptor micelles, the rate of transfer of the fluorophore from the donor to the acceptor was measured by monitoring the release in self quenching when its concentration in donor decreased over time.

• Journal of the Korean Society of Food Science and Nutrition
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• v.21 no.4
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• pp.381-385
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• 1992

The effect of antioxidant activity of soyasaponin on the liposomal phospholipid membrane were investigated by spectrophotometry. The oxidation index and oxidation rate of ${\alpha}-tocopherol$ containing egg phosphatidylcholine (EPC) liposomes were markedly decreased in the presence of soyasaponin relative to those of purephospholipid liposmes. ${\alpha}-tocopherol$ containing liposomes delayed the oxidation of liposomes. Especially soyasaponin stimulated the antioxidant activity of ${\alpha}-tocopheroal$ in liposomes. These results indicates that soyasaponin in liposomes had some additive effect on antioxidant of ${\alpha}-tocopherol$ toward liposomes.

• Archives of Pharmacal Research
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• v.10 no.2
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• pp.94-99
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• 1987

By using the former equation (8), we modified the equation which can show the dissimilar osmotic behavior of liposome with composition change. The slope of the new equation was presented as the ratio of osmotically active volume (V$_{act}$= ) to the total volume (V$_{totel}$= $_{acl}$+ V$_{dead}$ ; V$_{dead}$ is osmotically inactive volume) of loposomes, we defined is as a Z-value, which can elucidate the dissimilarity of the osmotic activity of multilamellar liposomes with the change of phospholipid composition and the differences of physicochemical properties of liposomes. Z-value was applied for studying the physico-chemical properties of liposomal membrane. The factor that affects on the Z-value was not the lipid concentration of liposome stock dispersion but the lipid composition of liposomal membrane. As the content of dicetylphosphate, the negative charged phospholipid, was increased, the osmotic activity, represented by Z-value, of multilamellar liposome was decreased. Using the hypertonic conditions (shrinking region), Z-value steadily increased and reached a maximum at 10 mole percent cholesterol with increasing the cholesterol content.

• Journal of Life Science
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• v.26 no.8
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• pp.875-880
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• 2016

The plasma membrane plays a crucial role in relaying signals from the outside environment to the inside of the cells. In eukaryotic cells, the inner leaflets of the plasma membrane are composed mostly of phospholipids, including phosphatidylethanolamine (PE), phosphatidylserine (PS), and phosphatidylinositides (PIs). In this study, we tried to analyze the morphological changes induced by EGFP-fused membrane binding proteins, which are targeted to the plasma membrane via specific phospholipids binding. As a result, we found that overexpression of EGFP-P4M-SidM, a specific PI4P binding protein, or EGFP alone, did not induce any morphological changes. On the other hand, overexpression of EGFP-PLCδ1(PH), which is a specific PI(4,5)P₂ binding protein, EGFP-AKT1(PH) which binds to PI(3,4,5)P₃, or EGFP-OSH2(PH)×2 which binds to PI4P and PI(4,5)P₂, could induce the filopodia and lamilapodia formation as well as cell shrinkage. Overexpression of Lact-C2-EGFP which is a specific PS-binding probe, EGFP fused Aplysia phosphodiesterase 4 (ApPDE4) long-form (L(N20)-EGFP) which is localized to the plasma membrane via hydrophobic interaction, or EGFP fused Aplysia PDE4 short-form (S(N-UCR1-2)-EGFP) which is localized to the plasma membrane via electrostatic interaction, could induce cell shrinkage, but not filopodia or lamilapodia formation. Taken together, our data support that the different phospholipid bindings in the plasma membrane could induce different characteristic morphological changes. Thus, we can analyze, characterize, and classify the cellular morphological changes induced by the various phospholipid binding proteins.

• Microbiology and Biotechnology Letters
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• v.22 no.1
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• pp.1-6
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• 1994

We have studied the relation between Ca$^{2+}$-ATPase and trigger peptidase(TPase) which are membeane protein well known as their significant role for signal transduction of mating pheromone in heterobasidiomycetous yeast. Rhodosporidium toruloides. We found out that there were Ca $^{2+}$-ATPase and TPase together in isolated calmodulim binding protein(CBP), usion calmodulin affinity column chromatography after solubilization of mation type a cell membrane protein, and that the dependence of enzyme activity of both the enzymes on Ca$^{2+}$, phospholipid and nonionic detergent are similar. However, Ca$^{2+}$-ATPase hed quite absolute dependence on calmodulin and, on the other hand, TPase didn't have any dependence. Judging from the fact that there are both enzymes in CBP which the dependence of calmodulin are quite different, we found out that both enzymes were made to their compound and existed in mating type a cell membrane.