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

Biochim Biophys Acta. 2000 Dec 20;1509(1-2):7-13. doi: 10.1016/s0005-2736(00)00349-7.

Abstract

To date, two different transporters that are capable of transporting alpha-(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 alpha-[(14)C](methylamino)isobutyric acid and [(3)H]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 K(0. 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.

Publication types

  • Comparative Study

MeSH terms

  • Alanine / metabolism
  • Amino Acid Sequence
  • Amino Acid Transport Systems
  • Animals
  • Carrier Proteins / chemistry
  • Carrier Proteins / genetics*
  • Carrier Proteins / metabolism
  • Cloning, Molecular
  • DNA, Complementary / biosynthesis
  • Electrophysiology
  • Gene Library
  • Liver / metabolism*
  • Molecular Sequence Data
  • Muscle, Skeletal / metabolism*
  • Oocytes / metabolism
  • Rats
  • Sequence Homology, Amino Acid
  • Substrate Specificity
  • Xenopus laevis
  • beta-Alanine / analogs & derivatives*
  • beta-Alanine / metabolism

Substances

  • Amino Acid Transport Systems
  • Carrier Proteins
  • DNA, Complementary
  • beta-Alanine
  • 2,2-dimethyl-beta-alanine
  • Alanine

Associated data

  • GENBANK/AF295535