Ammonia transporter

Ammonia transporters are structurally related membrane transport proteins called Amt proteins (ammonia transporters, bacteria and plants), methylammonium/ammonium permeases (MEPs, in yeast) or RhAG, RhBG, and RhCG Rh family members in mammals. The RhAG, RhBG and RhCG proteins constitute solute carrier family 42. The three dimensional structure of the ammonia transport protein AmtB from Escherichia coli was determined by x-ray crystallography. The structure has a hydrophobic ammonia channel. The human RhCG ammonia transporter was found to have a similar ammonia-conducting channel structure. It was proposed that the erythrocyte Rh complex is a heterotrimer of RhAG, RhD, and RhCE subunits in which RhD and RhCE might play roles in anchoring the ammonia-conducting RhAG subunit to the cytoskeleton. Based on reconstitution experiments, purified RhCG subunits alone can function to transport ammonia. RhCG is required for normal acid excretion by the mouse kidney and epididymis.