title: The B°AT1 amino acid transporter from rat kidney reconstituted in liposomes: kinetics and inactivation by methylmercury.
abstract: The neutral amino acid transporter B°-like from rat kidney, previously reconstituted in liposomes, was identified as B°AT1 by a specific antibody. Collectrin was present in the brush-border extract but not in functionally active proteoliposomes, indicating that it was not required for the transport function. Neutral amino acids behaved as competitive inhibitors of the glutamine transport mediated by B°AT1 with half saturation constants ranging from 0.13 to 4.74mM. The intraliposomal half saturation constant for glutamine was 2.0mM. By a bisubstrate kinetic analysis of the glutamine-Na(+) cotransport, a random simultaneous mechanism was found. Methylmercury and HgCl(2) inhibited the transporter; the inhibition was reversed by dithioerythritol, Cys and, at a lower extent, N-acetylcysteine but not by S-carboxymethylcysteine. The IC(50) of the transporter for methylmercury and HgCl(2) was 1.88 and 1.75μM, respectively. The reagents behaved as non-competitive inhibitors toward both glutamine and Na(+) and no protection by glutamine or Na(+) was found for the two inhibitors.
authors.affiliation: Department of Cell Biology, University of Calabria, Arcavacata di Rende, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Oppedisano
authors.forename: Lorena
authors.initials: L
authors.lastname: Pochini
authors.forename: Stefan
authors.initials: S
authors.lastname: Bröer
authors.forename: Cesare
authors.initials: C
authors.lastname: Indiveri
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D026905:Amino Acid Transport Systems / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D020128:Inhibitory Concentration 50; D007668:Kidney / Q000378:metabolism*; D007700:Kinetics; D008767:Methylmercury Compounds / Q000494:pharmacology*; D008871:Microvilli / Q000378:metabolism; D021381:Protein Transport; D011510:Proteolipids; D051381:Rats; D012995:Solubility
chemical_list: D026905:Amino Acid Transport Systems; D008767:Methylmercury Compounds; D011510:Proteolipids; C020485:proteoliposomes; D000111:Acetylcysteine