Cystinuria-specific rBAT(R365W) mutation reveals two translocation pathways in the amino acid transporter rBAT-b0,+AT

Biochem J. 2004 Feb 1;377(Pt 3):665-74. doi: 10.1042/BJ20030956.


Apical reabsorption of dibasic amino acids and cystine in kidney is mediated by the heteromeric amino acid antiporter rBAT/b(0,+)AT (system b(0,+)). Mutations in rBAT cause cystinuria type A, whereas mutations in b(0,+)AT cause cystinuria type B. b(0,+)AT is the catalytic subunit, whereas it is believed that rBAT helps the routing of the rBAT/b(0,+)AT heterodimeric complex to the plasma membrane. In the present study, we have functionally characterized the cystinuria-specific R365W (Arg(365)-->Trp) mutation of human rBAT, which in addition to a trafficking defect, alters functional properties of the b(0,+) transporter. In oocytes, where human rBAT interacts with the endogenous b(0,+)AT subunit to form an active transporter, the rBAT(R365W) mutation caused a defect of arginine efflux without altering arginine influx or apparent affinities for intracellular or extracellular arginine. Transport of lysine or leucine remained unaffected. In HeLa cells, functional expression of rBAT(R365W)/b(0,+)AT was observed only at the permissive temperature of 33 degrees C. Under these conditions, the mutated transporter showed 50% reduction of arginine influx and a similar decreased accumulation of dibasic amino acids. Efflux of arginine through the rBAT(R365W)/b(0,+)AT holotransporter was completely abolished. This supports a two-translocation-pathway model for antiporter b(0,+), in which the efflux pathway in the rBAT(R365W)/b(0,+)AT holotransporter is defective for arginine translocation or dissociation. This is the first direct evidence that mutations in rBAT may modify transport properties of system b(0,+).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Substitution / genetics*
  • Amino Acid Substitution / physiology
  • Amino Acid Transport System ASC / physiology
  • Amino Acid Transport Systems / genetics
  • Amino Acid Transport Systems / physiology
  • Amino Acid Transport Systems, Basic*
  • Animals
  • Arginine / genetics
  • Arginine / metabolism
  • Carrier Proteins / genetics*
  • Carrier Proteins / physiology
  • Cell Line, Tumor
  • Cystinuria / genetics*
  • Cystinuria / physiopathology
  • Female
  • HeLa Cells / chemistry
  • HeLa Cells / metabolism
  • Humans
  • Membrane Glycoproteins / genetics*
  • Membrane Glycoproteins / physiology
  • Minor Histocompatibility Antigens
  • Mutation / genetics*
  • Mutation / physiology
  • Oocytes / chemistry
  • Oocytes / metabolism
  • Transfection
  • Tryptophan / genetics
  • Xenopus laevis


  • Amino Acid Transport System ASC
  • Amino Acid Transport Systems
  • Amino Acid Transport Systems, Basic
  • Carrier Proteins
  • Membrane Glycoproteins
  • Minor Histocompatibility Antigens
  • SLC1A5 protein, human
  • SLC7A9 protein, human
  • Tryptophan
  • Arginine