Fatty Acid Fueled Transmembrane Chloride Transport

Generation of chemical gradients across biological membranes of cellular compartments is a hallmark of all living systems. Here we report a proof of -concept prototype transmembrane pumping system in liposomes. The pump uses fatty acid to fuel chloride transport, thus generating a transmembrane chloride gradient. Addition of fatty acid to phospholipid vesicles generates a transmembrane pH gradient (pH(in) < pH(out)), and this electrochemical H+ potential is harnessed by an anionophore to drive chloride efflux via H+/Cl- cotransport. Further addition of fatty acid efficiently fuels the system to continuously drive chloride transport against the concentration gradient, up to [Cl-](in) 65 mM vertical bar [Cl-](out) 100 mM, and is 1400 times more efficient than using an external fuel. Based on our findings from dissecting the H+/Cl- flux process with the use of different liposomal fluorescence assays, and supported by additional liposome-based C-13 NMR and DLS studies; we proposed that the presence of an anionophore can induce asymmetric distribution of fatty acid, and contribute to another Cl- flux mechanism in this system.