Electrogenic amino acid exchange via the rBAT transporter.
A cDNA clone was isolated from rabbit renal cortex using DNA-mediated expression cloning, which caused alanine-dependent outward currents when expressed in Xenopus oocytes. The cDNA encodes rBAT, a Na-independent amino acid transporter previously cloned elsewhere. Exposure of cDNA-injected oocytes to neutral amino acids led to voltage-dependent outward currents, but inward currents were seen upon exposure to basic amino acids. Assuming one charge/alanine, the outward current represented 38% of the rate of uptake of radiolabelled alanine, and was significantly reduced by prolonged preincubation of oocytes in 5 mM alanine. The currents were shown to be due to countertransport of basic amino acids for external amino acids using the cut-open oocyte system. This transport represents a major mode of action of this protein, and may help in defining a physiological role for rBAT in the apical membrane of renal and intestinal cells.
Coady
M J
MJ
Groupe de recherche en transport membranaire, Université de Montréal, Que., Canada.
Jalal
F
F
Chen
X
X
Lemay
G
G
Berteloot
A
A
Lapointe
J Y
JY
D000409:Alanine / Q000378:metabolism / Q000494:pharmacology; D026923:Amino Acid Transport Systems, Basic; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001120:Arginine / Q000378:metabolism / Q000494:pharmacology; D001483:Base Sequence; D001692:Biological Transport; D002352:Carrier Proteins / Q000096:biosynthesis / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary; D005260:Female; D007672:Kidney Cortex / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology*; D011817:Rabbits; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D014982:Xenopus laevis
D026923:Amino Acid Transport Systems, Basic; D000596:Amino Acids; D002352:Carrier Proteins; D018076:DNA, Complementary; D008562:Membrane Glycoproteins; D011994:Recombinant Proteins; C082087:rBAT protein, Oryctolagus cuniculus; D001120:Arginine; D000409:Alanine