Controlled fluid transport using ATP-powered protein pumps

Abstract

Plants have the ability to move fluids using the chemical energy available with bio-fuels.The energy released by the cleavage of a terminal phosphate ion during the hydrolysis of abio-fuel assists the transport of ions and fluids in cellular homeostasis. The device discussedin this paper uses protein pumps cultured from plant cells to move fluid across a membranebarrier for controllable fluid transport. This paper demonstrates the ability to reconstitutea protein pump extracted from a plant cell on a supported bilayer lipid membrane (BLM)and use the pump to transport fluid expending adenosine triphoshate (ATP). TheAtSUT4 protein used in this demonstration is cultured from Arabidopsis thaliana.This protein transporter moves a proton and a sucrose molecule in the presenceof an applied proton gradient or by using the energy released from adenosinetriphosphate’s hydrolysis reaction. The BLM supporting the AtSUT4 is formed from1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-L-Serine] (sodium salt) (POPS),1-Palmitoyl-2-Oleoyl-sn-Glycero-3-Phosphoethanolamine (POPE) lipids supported on aporous lead silicate glass plate. The BLM is formed with the transporter and theATP-phosphohydrolase (red beet ATPase) enzyme, and the ATP required for thereaction is added as a magnesium salt on one side of the membrane. The ATPhydrolysis reaction provides the required energy for transporting a proton–sucrosemolecule through the protein pump. It is observed that there is no fluid transportin the absence of the enzyme and the amount of fluid transported through themembrane is dependent on the amount of enzyme reconstituted in the BLM for a fixedsucrose concentration. This demonstrates the dependence of the fluid flux on theATP hydrolysis reaction catalyzed by the ATP-ase enzyme. The dependenceof fluid flux on the amount of ATP-ase provides convincing evidence that thebiochemical reaction is producing the fluid transport. The fluid flux resulting from theATP-powered transport is observed to be higher than the rates observed witha proton concentration gradient driven transport reported in our earlier work.