CHAPEL HILL - For the first time, scientists have succeeded in mapping the structure of an ion pump in cells' plasma membrane - the "bag" that holds human and animal cells together and separates them from neighboring cells. The researchers did it by crystallizing the membrane and studying it under electron microscopes.
Their work is a basic science breakthrough, the investigators say, because of the great difficulty involved and the importance of membranes, which control many key bodily functions.
"Before you can understand how something in the body works, you have to know what its structure is at the atomic level, and that's what we have been investigating," said Dr. Gene A. Scarborough, professor of pharmacology at the University of North Carolina at Chapel Hill School of Medicine. "The ion pump we studied is especially important because it is part of a family of membrane proteins that regulate blood pressure, heart function, nerve conduction and acid secretion."
A report on the findings just appeared in Nature, the top British biological journal. Besides Scarborough, authors are Dr. Manfred Auer and Werner Kuhlbrandt of the Max Planck Institute for Biophysics in Frankfurt, Germany.
"Membranes and the pumps within them are important because they help keep the good stuff inside cells and the bad stuff out," Scarborough said. "But to see the structure of membrane pumps, you have to crystallize them. That is what we have done, and we are getting very close to atomic resolution."
In creating their 3-D "map," the researchers used a detergent-like compound to overcome a stubborn technical difficulty. The problem was that unlike most other proteins, cell membrane proteins are embedded in a natural greasy substance that makes growing crystals of them nearly impossible.