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Published on: October 30, 2014
Amino acid transport system A resembles system N in sequence but differs in mechanism
R J Reimer1, F A Chaudhry, A T Gray
1Department of Neurology, University of California, San Francisco School of Medicine, 513 Parnassus Avenue, San Francisco, CA 94143.
Abstract:
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.
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