Urea transport and Kidd blood groups.

The gene encoding for the human erythrocyte urea transporter (HUT11 clone) has recently been cloned (Olives et al., J. Biol. Chem., 269, 3/649, 1994). It has been localized at 18q12-q21, like the Kidd blood group gene. In vitro translation experiments indicated that cDNA HUT11 could induce the synthesis of a 36 kDa protein which can be immunoprecipitated by an anti-Jk3 antibody (a human antibody produced by Jk(a-b-) individuals). This antibody also precipitates a 46-60 kDa protein from human red blood cells, except from those with Jk(a-b-) phenotype. After N-glycanase digestion, the length of the glycoprotein was reduced from 46-60 kDa to 36 kDa. Moreover, a rabbit antibody directed against the N-terminal end of HUT11 protein reacts in western-blot with 46-60 kDa proteins present in all human red blood cells, except those with Jk(a-b-) phenotype. Jk(a-b-) cells have neither Kidd protein nor HUT11 urea transporter and they are characterized by a selective defect of urea transport whereas water transport and aquaporin-1 associated Colton antigens are normally expressed. All these findings provide evidence that the Kidd locus encodes for the human erythrocyte urea transporter, offering new prospects for biological study of urea transporters and their tissue-specific regulation.