Unexpected expression of carbonic anhydrase I and selenium-binding protein as the only major non-heme proteins in erythrocytes of the subterranean mole rat (Spalax ehrenbergi)

Chromatographic separation of the non-heme proteins from the erythrocytes of the subterranean mole rat belonging to the superspecies Spalax ehrenbergi from Israel revealed two major peaks. On sequence analyses, the larger peak corresponded to a 56 kDa selenium-binding protein (SeBP) previously characterized from mouse and human liver, and the second peak to the low-activity carbonic anhydrase (CA) isozyme, CA I. There was no evidence of the high-activity CA II isozyme normally found in the red cells of all amniotes tested to date. Thus, the mole rat appears to be the first mammalian species to express both a SeBP and the low-activity CA I isozyme, as the major non-heme proteins in its red blood cells. It is possible that the absence of the high-activity CA II isozyme may be advantageous to the mole rat in adapting to the low O₂ and high CO₂ environment of its underground burrows. It is also likely that the 56 kDa SeBP may play an important adaptive role in the physiology of the red cell.