Catalysis of the transfer of ammonium from one side of a membrane to the other. Ammonium is the cation NH4+ which is formed from N2 by root-nodule bacteria in leguminous plants and is an excretory product in ammonotelic animals.
J. Biol. Chem. 269, 31649-31652 (1994)[PubMed:7989337]
A rapid passive urea transport has been previously described in the mammalian renal inner medullary collecting duct epithelial cells and in mammalian erythrocytes. Recently, a vasopressin-regulated urea transporter (UT2) has been cloned from a rabbit kidney medullary cDNA library (You, G., Smith, C. P., Kanai, Y., Lee, W. S., Stelzner, M., and Hediger, M. A. (1993) Nature 365, 844-847). We now report the cloning and characterization of a complementary DNA (HUT11) encoding an urea transporter isolated from a human bone marrow library. It encodes a 43,000-Da polypeptide of 391 amino acids that exhibited 63% sequence identity with the rabbit urea transporter and a similar membrane topology. HUT11 carries 2 putative glycosylation sites and 10 cysteines, of which only 7 are conserved at an equivalent position in UT2. HUT11 transcripts have been identified in human erythroid and renal tissues. Expression studies in Xenopus oocytes demonstrated that HUT11 mediates a facilitated urea transport that was inhibited, as described in mammalian erythrocytes, by very low concentrations of phloretin, p-chloromercuribenzene sulfonate, and urea analogues. No unidirectional movements of charged molecules, glycerol, or water were associated with HUT11 expression in oocytes. These findings suggest that HUT11 is most likely responsible for the facilitated urea transport in human red blood cells.
Protein involved in the transport of a molecule (metabolite, protein, etc), a ion or an electron across cell membranes, inside the cell or in a tissue fluid.
Protein belonging to the set of cell surface antigens found chiefly, but not solely, on blood cells. More than fifteen different blood group systems are recognised in humans. In most cases the antigenic determinant resides in the carbohydrate chains of membrane glycoproteins or glycolipids.
A reference proteome is a set of protein sequences derived from a complete proteome which constitutes a defined standard for a particular user community. Reference proteomes are manually defined according to a number of criteria. They cover the proteomes of well- studied model organisms and other proteomes of interest for biomedical and biotechnological research. Reference proteomes have been selected to provide broad coverage of the tree of life, and constitute a representative cross-section of the taxonomic diversity to be found within UniProtKB.
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