Diffusion of Mn2+ ions into liposomes mediated by phosphatidate and monitored by the activation of an encapsulated enzymatic system.
Transbilayer diffusion of Mn2+ ions occurred in liposomes formed from dipalmitoyl-phosphatidylcholine or egg-yolk phosphatidylcholine and egg-yolk phosphatidate (molar ratio 2:1) containing DNA and DNase I within their aqueous compartments. Cation diffusion was demonstrated by the hydrolytic activity of DNase I, activated by the Mn2+ ions that diffused into the vesicles, and this was confirmed by light scattering. Phosphatidate, a cone-shaped lipid which has been synthesized under simulated prebiotic conditions, was necessary for cation diffusion across the liposome membranes. Such liposomes represent a simple precellular system that interchanges cations with the surroundings and provides a microenvironment for enzymatic reactions, as evidenced by the hydrolysis of DNA by DNase I inside these closed lipid compartments.
Baeza
I
I
Departamento de Bioquímica, Escuela Nacional de Ciencias Biológicas, México, D.F. México.
Ibáñez
M
M
Santiago
J C
JC
Argüello
C
C
Wong
C
C
Oró
J
J
D002412:Cations / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D003850:Deoxyribonuclease I / Q000378:metabolism; D004058:Diffusion; D004789:Enzyme Activation; D008027:Light; D008051:Lipid Bilayers / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism*; D010539:Permeability; D010712:Phosphatidic Acids / Q000378:metabolism*; D012542:Scattering, Radiation; D013696:Temperature
D002412:Cations; D008051:Lipid Bilayers; D008081:Liposomes; D010712:Phosphatidic Acids; D004247:DNA; D003850:Deoxyribonuclease I; D008274:Magnesium