Characterization of mouse amino acid transporter B0AT1 (slc6a19).
The mechanism of the mouse (m)B0AT1 (slc6a19) transporter was studied in detail using two electrode voltage-clamp techniques and tracer studies in the Xenopus oocyte expression system. All neutral amino acids induced inward currents at physiological potentials, but large neutral non-aromatic amino acids were the preferred substrates of mB0AT1. Substrates were transported with K0.5 values ranging from approx. 1 mM to approx. 10 mM. The transporter mediates Na+-amino acid co-transport with a stoichiometry of 1:1. No other ions were involved in the transport mechanism. An increase in the extracellular Na+ concentration reduced the K0.5 for leucine, and vice versa. Moreover, the K0.5 values and Vmax values of both substrates varied with the membrane potential. As a result, K0.5 and Vmax values are a complex function of the concentration of substrate and co-substrate and the membrane potential. A model is presented assuming random binding order and a positive charge associated with the ternary [Na+-substrate-transporter] complex, which is consistent with the experimental data.
Böhmer
Christoph
C
Physiologisches Institut, Universität Tübingen, 72076 Tübingen, Germany.
Bröer
Angelika
A
Munzinger
Michael
M
Kowalczuk
Sonja
S
Rasko
John E J
JE
Lang
Florian
F
Bröer
Stefan
S
D026905:Amino Acid Transport Systems / Q000737:chemistry* / Q000378:metabolism*; D026921:Amino Acid Transport Systems, Neutral / Q000737:chemistry / Q000378:metabolism*; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active; D007700:Kinetics; D008564:Membrane Potentials; D051379:Mice; D009865:Oocytes; D013379:Substrate Specificity; D014981:Xenopus
D026905:Amino Acid Transport Systems; D026921:Amino Acid Transport Systems, Neutral; D000596:Amino Acids; C505021:SLC6A19 protein, mouse