Wednesday, October 8, 2003
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Nobel Prize in Chemistry Honors Work on Movement of Water and Salts Across Cell MembranesBy LILA GUTERMAN
This year's Nobel Prize in Chemistry was awarded this morning to two American biochemists, for their discoveries about how water and salts move into and out of living cells. The discoveries hold importance for the study of many diseases and demonstrate "how contemporary biochemistry reaches down to the atomic level in its quest to understand the fundamental processes of life," said a citation issued by the Royal Swedish Academy of Sciences. The two laureates, who will share $1.3-million and will receive their awards in December, are Peter Agre, 54, a professor of biological chemistry and of medicine at the Johns Hopkins University, and Roderick MacKinnon, 47, a professor of molecular neurobiology and biophysics at Rockefeller University. Scientists have understood since the mid-19th century that cells must have ways of controlling how much water travels into and out of their interiors, but until 1988, no one had found the molecule they used to do it. Dr. Agre isolated the protein that sits in the cell's membrane -- which is oily and therefore should repel water -- and guides water molecules through. In the early 1990s, Dr. Agre proved that the function of the protein, known as aquaporin, was indeed water transport by comparing cells that contained the molecule in their membranes with other cells that were identical in every way except that they lacked aquaporin. When he put the the cells in a water solution, only those containing aquaporin swelled up. Since that discovery, aquaporin-like proteins have been found in every form of life; human beings have at least 11 different proteins in the family. Their importance is most obvious in the kidney, which filters and reabsorbs the body's water content every 45 minutes, for a total of about 150 to 200 liters a day. Only about one liter of water actually leaves the body as urine. Faulty water-transport proteins can lead to fluid retention, while the antidiuretic hormone called vasopressin leads to larger numbers of an aquaporin protein in the kidney's cell membranes. Cells also regulate how other molecules and electrically charged salts, or ions, move through their membranes. The movement of ions controls how cells communicate; the ions act as signals that trigger bodily functions, from thoughts to muscle contractions. In 1998, Dr. MacKinnon used X-ray crystallography to produce the first detailed images showing the structure of a protein that transports ions into or out of a cell, or stops them in their tracks. In the crystal structure, he could see not only the protein but also the ions moving through it. Dr. MacKinnon demonstrated how the protein, called KcsA, allows potassium ions to move through the membrane, but prevents the transport of sodium ions, which behave similarly, in a chemical sense, but are smaller than potassium ions. Last year, he also determined how the cell membrane opens or closes the ion channel to potassium ions. Because of the importance of signaling using ions in the brain and other organs, ion-channel proteins that do not function can cause serious diseases. Researchers now are looking at how drug candidates interact with ion-channel proteins. The full text of the academy's citation is available on the Nobel Web site.
Other news of 2003 Nobel Prizes:
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 U. of California to review admissions issues systemwide; report questions practices at Berkeley 2 scholars who revolutionized statistical modeling are awarded the Nobel in economics Nobel Prize in Chemistry honors work on movement of water and salts across cell membranes Californians reject ballot measure that would ban racial data NCAA proposes new gauge for graduation rates that it says is fairer and more accurate President of Loyola U. New Orleans resigns after allegation of sexual misconduct Survey sets information-technology benchmarks for campuses, and suggests a lingering 'digital divide' |
Copyright © 2003 by The Chronicle of Higher Education