Do you know your blood type? No matter what type it ends in either a "positive" or "negative", which refers to the type of so-called Rhesus you carry. Although scientists have been typing blood for decades, nobody knew the purpose of Rh proteins. Now a study shows that proteins carrying ammonium, a toxic by-product of energy metabolism, and may keep the level pH balanced blood.
So far, the Rh protein that dot the surface of red blood cells were known to the problems they can cause blood transfusions and pregnancy. If a patient receives a transfusion with Rh proteins mismatched, the antibodies accumulate and attack the new blood. Similarly, an Rh positive fetus can trigger an immune response in an Rh negative mother, if untreated, can injure or kill the fetus.
The link between the Rh protein and transport of ammonium was unexpected. It several years ago, a yeast research team led by Bruno André of the Free University of Brussels, Belgium, identified yeast proteins that transport ammonium. They entered the gene sequence that codes carriers in a database of the genome and saw that it closely matched the genes for Rh proteins in humans. To find out if the Rh proteins perform a similar function, the team knocked ammonium transporters genes in yeast and replace them with human Rh protein genes. The Rh proteins ammonium pumped out of cells, they report in the November issue of Nature Genetics .
"This is the first solid evidence for a biological role" for Rh proteins, said hematologist Peter Agre of Johns Hopkins University. Andrew and his team suggest that red blood cells pick up the excess ammonium in blood and deliver it to the kidneys, which filter out. This system clear the blood of toxic ammonium and maintain the pH, they claim.
Related Sites
the André team website
for more information on the Rh factors and pregnancy
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