The enzyme creates energy through respiration and uses that energy to pump ions out of the cell, electrically charging the cell membrane and providing power for all the functions of the cell. Unlike similar enzymes found in many animals and bacteria, Na+-NQR pumps sodium ions out of the cell, rather than protons.
Barquera's paper in PNAS describes the mechanism the enzyme uses to convert energy using sodium ions.
"Na+-NQR plays the same role as human respiratory proteins but it is much smaller," Barquera said. "We want to understand how it works, how it produces energy. If we understand how Na+-NQR works, we can learn the basic principles used by living organisms to convert energy and transport ions."
Researchers studied the enzyme by removing it from the inner cell membrane and studying it in a solution. Na+-NQR, which prefers an environment of water and oil, flourished in a solution similar to detergent, which mimics the bacterial membrane.
"We have the enzyme off of the membrane with all of its components," Barquera said. Once isolated, the researchers observed the enzyme as it moved sodium from the inside to the outside of the cell.
Their study revealed the protein itself is moving the ions along a path through the cell membrane.
"It works in a very different way from enzymes in other bacteria and mitochondria. The catch and release of ions is done by movement of the protein," Barquera said.
Barquera said that, by modifying the protein in various ways, the researchers had identified the site on the protein where the ions begin and end their travel along the protein.
Next they want to map the route the ion takes along the protein.
"We can see the in and out site. Now we want to know the path," Barquera said.
|Contact: Mary Martialay|
Rensselaer Polytechnic Institute