Biomaterial Database

Kinetics of cholesterol and phospholipid exchange between mycoplasma membranes and lipid vesicles. 1987

R Bittman, and S Clejan

Department of Chemistry, Queens College of the City University of New York, Flushing 11367.

The following modifications in the lipid composition of Mycoplasma gallisepticum or M. capricolum membranes led to changes in the rates of [14C]cholesterol and [14C]phospholipid exchange between cell membranes and an excess of small unilamellar vesicles: 1) increase in the cholesterol/phospholipid molar ratio from 0.25 to 0.92; 2) incorporation of synthetic, cross-linked phosphatidylethanolamine (PE) derivatives, 3) incorporation of sphingomyelin (SPM); and 4) increase in the phosphatidylglycerol/cardiolipin ratio of M. capricolum cell membranes by supplementing the growth medium with 0.5 mM CaCl2 CaCl2, and decrease in this ratio by supplementing the growth medium with 0.5 mM CaCl2 and 20 micrograms/ml egg phosphatidylcholine or with isopalmitic acid. The rates of radiolabeled lipid exchange decreased when the content of cholesterol, cross-linked PE, or SPM increased, indicating an inverse correlation between exchange rate and membrane lipid order. This is consistent with an exchange mechanism that involves the slow dissolution of the lipid from the surface of the donor particle. Lipidic particles appeared in trypsin-treated M. capricolum membranes obtained from cells grown with both Ca2+ and PC, whereas the hexagonal-II phase appeared in membranes from cells grown with Ca2+. Cholesterol and phospholipid exchange rates were enhanced under the conditions in which the bilayer structure was destabilized by transitional states between the lamellar and hexagonal-II phases. Thus, mycoplasmas are well suited for examination of the influence of membrane lipid composition on rates of lipid exchange between membranes.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008081	Liposomes	Artificial, single or multilaminar vesicles (made from lecithins or other lipids) that are used for the delivery of a variety of biological molecules or molecular complexes to cells, for example, drug delivery and gene transfer. They are also used to study membranes and membrane proteins.	Niosomes,Transferosomes,Ultradeformable Liposomes,Liposomes, Ultra-deformable,Liposome,Liposome, Ultra-deformable,Liposome, Ultradeformable,Liposomes, Ultra deformable,Liposomes, Ultradeformable,Niosome,Transferosome,Ultra-deformable Liposome,Ultra-deformable Liposomes,Ultradeformable Liposome
D008561	Membrane Fusion	The adherence and merging of cell membranes, intracellular membranes, or artificial membranes to each other or to viruses, parasites, or interstitial particles through a variety of chemical and physical processes.	Fusion, Membrane,Fusions, Membrane,Membrane Fusions
D008563	Membrane Lipids	Lipids, predominantly phospholipids, cholesterol and small amounts of glycolipids found in membranes including cellular and intracellular membranes. These lipids may be arranged in bilayers in the membranes with integral proteins between the layers and peripheral proteins attached to the outside. Membrane lipids are required for active transport, several enzymatic activities and membrane formation.	Cell Membrane Lipid,Cell Membrane Lipids,Membrane Lipid,Lipid, Cell Membrane,Lipid, Membrane,Lipids, Cell Membrane,Lipids, Membrane,Membrane Lipid, Cell,Membrane Lipids, Cell
D009174	Mycoplasma	A genus of gram-negative, mostly facultatively anaerobic bacteria in the family MYCOPLASMATACEAE. The cells are bounded by a PLASMA MEMBRANE and lack a true CELL WALL. Its organisms are pathogens found on the MUCOUS MEMBRANES of humans, ANIMALS, and BIRDS.	Eperythrozoon,Haemobartonella,Mycoplasma putrefaciens,PPLO,Pleuropneumonia-Like Organisms,Pleuropneumonia Like Organisms
D010743	Phospholipids	Lipids containing one or more phosphate groups, particularly those derived from either glycerol (phosphoglycerides see GLYCEROPHOSPHOLIPIDS) or sphingosine (SPHINGOLIPIDS). They are polar lipids that are of great importance for the structure and function of cell membranes and are the most abundant of membrane lipids, although not stored in large amounts in the system.	Phosphatides,Phospholipid
D002122	Calcium Chloride	A salt used to replenish calcium levels, as an acid-producing diuretic, and as an antidote for magnesium poisoning.	Calcium Chloride Dihydrate,Calcium Chloride, Anhydrous
D002784	Cholesterol	The principal sterol of all higher animals, distributed in body tissues, especially the brain and spinal cord, and in animal fats and oils.	Epicholesterol
D003432	Cross-Linking Reagents	Reagents with two reactive groups, usually at opposite ends of the molecule, that are capable of reacting with and thereby forming bridges between side chains of amino acids in proteins; the locations of naturally reactive areas within proteins can thereby be identified; may also be used for other macromolecules, like glycoproteins, nucleic acids, or other.	Bifunctional Reagent,Bifunctional Reagents,Cross Linking Reagent,Crosslinking Reagent,Cross Linking Reagents,Crosslinking Reagents,Linking Reagent, Cross,Linking Reagents, Cross,Reagent, Bifunctional,Reagent, Cross Linking,Reagent, Crosslinking,Reagents, Bifunctional,Reagents, Cross Linking,Reagents, Cross-Linking,Reagents, Crosslinking
D013045	Species Specificity	The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.	Species Specificities,Specificities, Species,Specificity, Species