Gatekeeper protein pictured in profile.Gatekeeper In an H.323 IP telephony or video environment, a gatekeeper is a device that manages domains and provides call control. It is used to translate user names into IP addresses, to authenticate users and to manage network resources. 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 ion channel n. See channel. (right) should help clarify how the structure functions and may lead to better drug design, says the scientists who used X-ray crystallography X-ray crystallography, the study of crystal structures through X-ray diffraction techniques. When an X-ray beam bombards a crystalline lattice in a given orientation, the beam is scattered in a definite manner characterized by the atomic structure of the lattice. to image the channel. Ion channels, made of protein, regulate the flow of important ions through cell membranes Cell membrane The membrane that surrounds the cytoplasm of a cell; it is also called the plasma membrane or, in a more general sense, a unit membrane. This is a very thin, semifluid, sheetlike structure made of four continuous monolayers of molecules. , 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 The Laboratory of Molecular Biology (or LMB) is a research institute in Cambridge, England, which was at the forefront of the revolution in molecular biology which occurred in the 1950-60s. Since then it remains a major medical research laboratory with a much broader focus. in Cambridge, England, in the Nov. 17 NATURE The channel is shaped like an hourglass hourglass, glass instrument for measuring time, usually consisting of two bulbs united by a narrow neck. One bulb is filled with fine sand that runs through the neck into the other bulb in an hour's time. , 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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