Amino acid transport system A resembles system N in sequence but differs in mechanism.
Classical amino acid transport System A accounts for most of the Na(+)-dependent neutral amino acid uptake by mammalian cells. System A has also provided a paradigm for short- and long-term regulation by physiological stimuli. We now report the isolation of a cDNA encoding System A that shows close similarity to the recently identified System N transporter (SN1). The System A transporter (SA1) and SN1 share many functional characteristics, including a marked sensitivity to low pH, but, unlike SN1, SA1 does not mediate proton exchange. Transport mediated by SA1 is also electrogenic. Amino acid transport Systems A and N thus appear closely related in function as well as structure, but exhibit important differences in ionic coupling.
Reimer
R J
RJ
Department of Neurology, University of California, San Francisco School of Medicine, 513 Parnassus Avenue, San Francisco, CA 94143.
Chaudhry
F A
FA
Gray
A T
AT
Edwards
R H
RH
D000595:Amino Acid Sequence; D026905:Amino Acid Transport Systems; D026921:Amino Acid Transport Systems, Neutral; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D004594:Electrophysiology; D015723:Gene Library; D006801:Humans; D017403:In Situ Hybridization; D008564:Membrane Potentials; D026901:Membrane Transport Proteins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011522:Protons; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D017422:Sequence Analysis, DNA; D012964:Sodium / Q000378:metabolism; D014018:Tissue Distribution; D015091:beta-Alanine / Q000031:analogs & derivatives / Q000378:metabolism
D026905:Amino Acid Transport Systems; D026921:Amino Acid Transport Systems, Neutral; D000596:Amino Acids; D002352:Carrier Proteins; D026901:Membrane Transport Proteins; D011522:Protons; D011994:Recombinant Proteins; C403222:system N protein 1; D015091:beta-Alanine; C012924:2,2-dimethyl-beta-alanine; D012964:Sodium