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Unformatted text preview: AQUAPORIN WATER CHANNELS Nobel Lecture, December 8, 2003 by Peter Agre The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. Thank you very much. I am humbled, I am delighted; I am honored. This is every scientist’s dream: to give the Nobel Lecture in Stockholm. But I would not be honest if I did not tell you that I am having a little anxiety being on this platform. I have lectured a number of times in Sweden, and I thought I would share with you some events preceding a special lecture that I gave here a few years ago. Arriving at Arlanda Airport, I waited in line at the Pass Control behind a group of businessmen in suits with briefcases. I heard the first in line asked by the control officer to state the purpose of his visit to Sweden. When the man replied “business,” the officer approved and stamped his passport. One at a time, each stepped forward and was asked the same thing; each answered “business” and was approved. Eventually it was my turn, and I was dressed in rumpled clothes after spending the night in the Economy Minus section of an SAS jetliner. The officer asked me the purpose of my visit, and I said “I am here to give the von Euler Lecture at Karolinska Institute.” The officer immediately looked up, stared at me, and asked, “Are you nervous?” At that point I became intensely nervous and said “Yes, I am a little nervous.” The officer looked up again and stated “Well, you should be!” So if the lecturers look a little nervous, the problem is at Arlanda. INTRODUCTION I am going to talk about aquaporin water channels. We have studied these proteins for several years, and we now understand that they explain how wa- ter crosses biological membranes. Water is commonly regarded as the “sol- vent of life,” since our bodies are 70% water. All other vertebrates, inverte- brates, microbes, and plants are also primarily water. The organization of water within biological compartments is fundamental to life, and the aqua- porins serve as the plumbing systems for cells. Aquaporins explain how our brains secrete and absorb spinal fluid, how we can generate aqueous humor within our eyes, how we can secrete tears, saliva, sweat, and bile, and how our kidneys can concentrate urine so effectively. These proteins are fundamental to mammalian physiology, but they are also very important in the lives of microorganisms and plants. 184 I wish to discuss the background in order to give credit to the individuals who were in this field long before we joined the field. With the recognition of the lipid bilayer as the plasma membranes of cells back in the 1920’s, it was correctly proposed that water could move through the membrane simply by diffusing through the lipid bilayer. The current view is that the lipid bilayer has a finite permeability for water, but, in addition, a set of proteins exists that we now refer to as “aquaporins.” Their existence was suggested by a group of pioneers in the water transport field who preceded us by decades – people in-...
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- Spring '09
- aquaporin, water permeability, Søren Nielsen