The glutamine/amino acid transporter (ASCT2) reconstituted in liposomes: electrical nature of the glutamine/glutamate antiport.
The glutamine/amino acid transporter solubilized from rat renal apical plasma membrane (brush-border membrane) with C12E8 and reconstituted into liposomes has been previously identified as the ASCT2 transporter. The reconstituted transporter catalyses an antiport reaction in which extraliposomal glutamine and Na+ are cotransported in exchange with intraliposomal neutral amino acids. Differently from other neutral amino acid transporters, ASCT2 accepts also glutamate as substrate, as demonstrated by the glutamine/glutamate antiport measured in proteoliposomes. The electrical nature of the homologous glutamine/glutamine antiport and of the heterologous glutamine/glutamate antiport has been investigated by imposing a K+ diffusion potential (positive outside) across the proteoliposomal membrane in the presence of valinomycin. The membrane potential did not affect the glutamine/glutamine antiport whereas it stimulated about two fold the glutamine/glutamate antiport rate.
Oppedisano
Francesca
F
Department of Cell Biology, University of Calabria, Arcavacata di Rende, Italy.
Pochini
Lorena
L
Galluccio
Michele
M
Indiveri
Cesare
C
D026962:Amino Acid Transport System ASC / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology; D005971:Glutamates / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism*; D008081:Liposomes / Q000737:chemistry*; D008564:Membrane Potentials / Q000502:physiology; D015778:Minor Histocompatibility Antigens; D051381:Rats
D026962:Amino Acid Transport System ASC; D005971:Glutamates; D008081:Liposomes; D015778:Minor Histocompatibility Antigens; C498849:Slc1a5 protein, rat; D005973:Glutamine