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Ionophore-mediated loading of Ca2+ into large unilamellar vesicles in response to transmembrane pH gradients. 1994

J J Wheeler, and J A Veiro, and P R Cullis
Department of Biochemistry, University of British Columbia, Vancouver, Canada.

The Ca2+ translocating properties of the carboxylic ionophores A23187, ionomycin and lasolocid A (X537A) have been investigated by employing large unilamellar vesicles that exhibit a pH gradient (acidic interior). An analysis of Ca2+ uptake at equilibrium reveals that Ca2+ accumulation is an electroneutral process, whereby one Ca2+ ion is transported in for every two H+ ions transported out. A kinetic analysis shows that both A23187 and ionomycin transport Ca2+ in the form of a 1:1 cation:ionophore complex, whereas a 1:2 complex is observed for lasolocid A. The specificity of the ionophores for transporting Ca2+ is reflected by the influence of exterior Na+ ions that inhibit Ca2+ uptake for lasolocid A but do not influence ionomycin-mediated uptake.

UI MeSH Term Description Entries
D007476 Ionophores Chemical agents that increase the permeability of biological or artificial lipid membranes to specific ions. Most ionophores are relatively small organic molecules that act as mobile carriers within membranes or coalesce to form ion permeable channels across membranes. Many are antibiotics, and many act as uncoupling agents by short-circuiting the proton gradient across mitochondrial membranes. Ionophore
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
D008566 Membranes Thin layers of tissue which cover parts of the body, separate adjacent cavities, or connect adjacent structures. Membrane Tissue,Membrane,Membrane Tissues,Tissue, Membrane,Tissues, Membrane
D002118 Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D002412 Cations Positively charged atoms, radicals or groups of atoms which travel to the cathode or negative pole during electrolysis. Cation
D006863 Hydrogen-Ion Concentration The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D000001 Calcimycin An ionophorous, polyether antibiotic from Streptomyces chartreusensis. It binds and transports CALCIUM and other divalent cations across membranes and uncouples oxidative phosphorylation while inhibiting ATPase of rat liver mitochondria. The substance is used mostly as a biochemical tool to study the role of divalent cations in various biological systems. 4-Benzoxazolecarboxylic acid, 5-(methylamino)-2-((3,9,11-trimethyl-8-(1-methyl-2-oxo-2-(1H-pyrrol-2-yl)ethyl)-1,7-dioxaspiro(5.5)undec-2-yl)methyl)-, (6S-(6alpha(2S*,3S*),8beta(R*),9beta,11alpha))-,A-23187,A23187,Antibiotic A23187,A 23187,A23187, Antibiotic
D015759 Ionomycin A divalent calcium ionophore that is widely used as a tool to investigate the role of intracellular calcium in cellular processes. SQ-23377,SQ 23377,SQ23377

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