Controlled fluid transport using ATP-powered protein pumps

摘要

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 a bio-fuel assists the transport of ions and fluids in cellular homeostasis. The device discussed in this paper uses protein pumps cultured from plant cells to move fluid across a membrane barrier for controllable fluid transport. This paper demonstrates the ability to reconstitute a 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). The AtSUT4 protein used in this demonstration is cultured from Arabidopsis thaliana. This protein transporter moves a proton and a sucrose molecule in the presence of an applied proton gradient or by using the energy released from adenosine triphosphate's hydrolysis reaction. The BLM supporting the AtSUT4 is formed from 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-L-Serine]( sodium salt) ( POPS), 1-Palmitoyl-2-Oleoyl-sn-Glycero-3- Phosphoethanolamine ( POPE) lipids supported on a porous lead silicate glass plate. The BLM is formed with the transporter and the ATP-phosphohydrolase ( red beet ATPase) enzyme, and the ATP required for the reaction is added as a magnesium salt on one side of the membrane. The ATP hydrolysis reaction provides the required energy for transporting a proton-sucrose molecule through the protein pump. It is observed that there is no fluid transport in the absence of the enzyme and the amount of fluid transported through the membrane is dependent on the amount of enzyme reconstituted in the BLM for a fixed sucrose concentration. This demonstrates the dependence of the fluid flux on the ATP hydrolysis reaction catalyzed by the ATP-ase enzyme. The dependence of fluid flux on the amount of ATP-ase provides convincing evidence that the biochemical reaction is producing the fluid transport. The fluid flux resulting from the ATP-powered transport is observed to be higher than the rates observed with a proton concentration gradient driven transport reported in our earlier work.