Cold viruses enter cells without knocking.Two research teams have found the structure of a key part of a protein that common cold viruses use as a doorknob to enter cells. The protein protrudes from the membranes of cells that line the inside of blood vessels Blood vessels Tubular channels for blood transport, of which there are three principal types: arteries, capillaries, and veins. Only the larger arteries and veins in the body bear distinct names. . Ordinarily, it functions as a receptor, binding white blood cells White blood cells A group of several cell types that occur in the bloodstream and are essential for a properly functioning immune system. Mentioned in: Abscess Incision & Drainage, Bone Marrow Transplantation, Complement Deficiencies as part of a local immune or inflammatory response. However, rhinoviruses, which cause 70 percent of colds in humans, use the receptor to weasel weasel, name for certain small, lithe, carnivorous mammals of the family Mustelidae (weasel family). Members of this family are generally characterized by long bodies and necks, short legs, small rounded ears, and medium to long tails. their way inside cells. Knowing the structure of the receptor, called ICAM-1, may help scientists find new ways to combat the common cold by stopping rhinoviruses from binding to it. Even though about 100 different types of rhinoviruses exist, says Jordi Bella of Purdue University Purdue University (pərdy  `, -d`), main campus at West Lafayette, Ind. in West Lafayette, Ind., most of them enter cells the same way--via ICAM-1. The two groups, one led by Michael G. Rossmann of Purdue and the other by Timothy A. Springer of Harvard Medical School Harvard Medical School (HMS) is one of the graduate schools of Harvard University. It is a prestigious American medical school located in the Longwood Medical Area of the Mission Hill neighborhood of Boston, Massachusetts. in Boston, used X-ray crystallography on purified samples of the receptor to deduce the shape of two crucial sections of the molecule. Reports from both groups appear in the April 14 Proceedings of the National, Academy of Sciences. Overall, the findings are quite similar, says Springer, but the groups differ in their descriptions of the paired structure that the receptor molecules assume In the cell membrane 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. . ICAM-1 is a long protein with five segments. One end is embedded in the cell membrane, and the other binds rhinoviruses. Examining the two segments farthest from the cell membrane, the, Purdue and Harvard teams found the the protein strand of the outermost out·er·most adj. Most distant from the center or inside; outmost. outermost Adjective furthest from the centre or middle Adj. 1. segment forms loops to which the virus attaches. Another portion of the segment binds white blood cells, says Bella. Because rhinoviruses and white blood, cells attach to different parts of the receptor, potential therapies would conceivably block the action of the virus without harming the normal function of the receptor, he adds. The Purdue group is now trying to produce an image of the virus and the receptor linked together. Learning how the virus and ICAM-1 stick to each other is only the first step in understanding how rhinoviruses Infect cells, says Bella. In terms of developing therapies, "maybe it will be more powerful to intervene on the subsequent steps." |
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