Most cells in the body carry on their surface tiny pores through which potassium ions travel. In controlling the flow of these positively charged ions, the channels helps the cell maintain its electrical balance. One particular type of potassium channel, called Eag1, has been found in a number of cell types: in the neurons of the brain, in embryonic cells that generate muscle fiber, and in some tumor cells, where it’s thought to have a cancer-promoting effect. But it’s not yet clear how Eag1 differs from other potassium channels, or exactly how it works. A duo of researchers at The Rockefeller University has taken an early step toward finding an answer. Using Rockefeller’s new facility for cryo-electron microscopy, an advanced imaging technique in which samples are frozen then bombarded with electrons, they determined the structure of Eag1. Their results, which were published in the August 12, 2016 issue of Science, have provided the first 3-D structure of a molecule to be published from Rockefeller’s facility. The article is titled “Structure of the Voltage-Gated K+ Channel Eag1 Reveals an Alternative Voltage Sensing Mechanism.” As some other potassium channels, Eag1 opens when it senses a change in electrical potential, as happens when neurons send signals. The part of the channel that most interested the researchers is the section that spans the cell membrane. This section includes the sensors responsible for detecting electrical changes, and the segments that form the pore through which potassium passes. The rest of the channel is located inside the cell. The researchers also determined the structure of another molecule called calmodulin, which binds to Eag1 and holds it in a closed position.
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