Membrane topology of the rat kidney neutral and basic amino acid transporter Academic Article uri icon


MeSH Major

  • Amino Acid Transport Systems, Basic
  • Amino Acid Transport Systems, Neutral
  • Amino Acids
  • Carrier Proteins
  • Kidney
  • Membrane Proteins


  • A recently cloned rat kidney protein (NBAT) mediates the sodium-independent transport of neutral as well as basic amino acids and cystine when expressed in Xenopus laevis oocytes. The human equivalent of this transporter may be the one that is defective in cystinuria. Immunocytochemical studies have indicated that NBAT is primarily localized in the brush border membranes of rat kidney and intestinal epithelial cells, a localization consistent with its proposed role in amino acid transport. Two contrasting topological models have been proposed for NBAT: a four membrane-spanning domain (MSD) Nin-Cin model and a single MSD Nin-Cout model. We have investigated the topology of this membrane protein using two different approaches. One method was an immunofluorescent labeling technique in which intact or membrane-permeabilized cells expressing NBAT were probed with antibodies directed against putative extracellular and intracellular domains of the protein. In the second method, fragments generated by limited surface proteolysis of intact brush border membrane vesicles were subjected to immunoblot analysis using several site-specific antibodies. Both approaches yielded results consistent with a four MSD Nin-Cin topological model for NBAT.

publication date

  • November 11, 1994



  • Academic Article



  • eng

PubMed ID

  • 7926373

Additional Document Info

start page

  • 1069

end page

  • 74


  • 8


  • 13