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Gatekeeper protein pictured in profile.

Gatekeeper protein pictured in profile

Just as it's easier to understand how a lawnmower engine works if you take it apart yourself instead of looking at a bag of the pieces, understanding how a biological structure works often requires understanding how it is put together.

For this reason, the first clear side view of a cell membrane's ion channel (right) should help clarify how the structure functions and may lead to better drug design, says the scientists who used X-ray crystallography to image the channel.

Ion channels, made of protein, regulate the flow of important ions through cell membranes, allowing muscles to contract and nerve cells to transmit signals. Scientists have imaged such channels from the top down, but the new side view is the first with enough resolution to show where ion passage through the channel may be regulated, say Chikashi Toyoshima and Nigel Unwin of the medical Research Council Laboratory of Molecular Biology in Cambridge, England, in the Nov. 17 NATURE

The channel is shaped like an hourglass, with the ions from outside the cell first entering the long opening at the top of the image. In the middle of the five-protein structure there is a much narrower gap, too small to be seen on the image, where ion flow is probably regulated, Unwin says. At the bottom end there sits a protein that is not part of the channel but may serve as some sort of fence, he says. "Before, we didn't know where the protein fit in," he adds. Researchers might be able to design drugs that regulate nerve signals by blocking the channel opening, Unwin suggests.
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Title Annotation:cell membrane ion channel
Author:Vaughan, Christopher
Publication:Science News
Date:Nov 19, 1988
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