Bruno Andre, of the Universite Libre de Bruxelles (Belgium), Baya Cherif-Zahar, of the Institut National de la Transfusion Sanguine (Paris, France), and colleagues have demonstrated that a Rhesus (Rh) blood-group antigen functions as an ammonium transporter (Nature Genetics, 01 Nov 2000). This is a new and unexpected function for these molecules known only for their adverse immunological effects during pregnancy or transfusion. This is also the first specific ammonium transport system to be described in humans.
Rh antigens, along with antigens of the ABO system, must be matched between donor and recipient to prevent severe immunological reactions during blood transfusion. Rh antigen mismatch between mother and father can also cause the death of their newborn child if blood-testing and preventive injections of anti-Rh immunoglobulins are not performed. Joseph Heitman, of Duke University, and Peter Agre, of Johns Hopkins University, explain in their News & Views article the fortuitous role that a Maccacus rhesus monkey played during the discovery of the antigens to which it gave its name, 60 years ago. The Rh antigens are proteins known to form complexes on the surface of red blood cells, but their normal biochemical function had been unknown. Researchers found that the Rh antigens had amino acid sequences similar to some yeast proteins involved in the transport of ammonium. They tested whether they could function as such by introducing the human Rh-AG protein into mutant yeast cells deficient in all their ammonium transporters. They showed that the human protein could replace their yeast homologues. This strongly suggests that one normal function of the human Rh complex is to transport ammonium. Such transporters were not previously known in humans and may have an important role in controlling our pH or nitrogen balances, not only in red blood cells but in liver and kidney as well. CONTACTS: (Author) Dr. Bruno Andre Universite Libre de Bruxelles Bruxelles, Belgium Telephone: (32) 2 650 9958 Fax: (32) 2 650 9950 E-mail: bran@ulb.ac.be (News & Views) Dr. Joseph Heitman Duke University Medical Center Howard Hughes Medical Institute Department of Genetics Durham, North Carolina, USA Telephone: +1 (919) 684-2824 Fax: +1 (919) 684-5458 E-mail: heitm001@mc.duke.edu
Dr. Peter Agre Johns Hopkins University Medical School Dept of Cell Biology & Anatomy Baltimore, Maryland, USA Telephone: +1 (410) 955-7049 Fax: +1 (410) 955 3149 (C) Nature Genetics press release.
Message posted by: Trevor M. D'Souza
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