Structure and function of ATA3, a new subtype of amino acid transport system A, primarily expressed in the liver and skeletal muscle

Mitsuru Sugawara, Takeo Nakanishi, You Jun Fei, Robert G. Martindale, Malliga E. Ganapathy, Frederick H. Leibach, Vadivel Ganapathy

Research output: Contribution to journalArticle

117 Scopus citations

Abstract

To date, two different transporters that are capable of transporting α-(methylamino)isobutyric acid, the specific substrate for amino acid transport system A, have been cloned. These two transporters are known as ATA1 and ATA2. We have cloned a third transporter that is able to transport the system A-specific substrate. This new transporter, cloned from rat skeletal muscle and designated rATA3, consists of 547 amino acids and has a high degree of homology to rat ATA1 (47% identity) and rat ATA2 (57% identity). rATA3 mRNA is present only in the liver and skeletal muscle. When expressed in Xenopus laevis oocytes, rATA3 mediates the transport of α-[14C](methylamino)isobutyric acid and [3H]alanine. With the two-microelectrode voltage clamp technique, we have shown that exposure of rATA3-expressing oocytes to neutral, short-chain aliphatic amino acids induces inward currents. The amino acid-induced current is Na+-dependent and pH-dependent. Analysis of the currents with alanine as the substrate has shown that the K0.5 for alanine (i.e., concentration of the amino acid yielding half-maximal current) is 4.2 ± 0.1 mM and that the Na+:alanine stoichiometry is 1:1. (C) 2000 Elsevier Science B.V.

Original languageEnglish (US)
Pages (from-to)7-13
Number of pages7
JournalBiochimica et Biophysica Acta - Biomembranes
Volume1509
Issue number1-2
DOIs
StatePublished - Dec 20 2000

Keywords

  • Amino acid transporter A3
  • Electrophysiology
  • Liver
  • Rat
  • Skeletal muscle
  • System A

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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