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System L: heteromeric exchangers of large, neutral amino acids involved in directional transport.
Journal article

System L: heteromeric exchangers of large, neutral amino acids involved in directional transport.

  • Verrey F University of Zurich, Institute of Physiology, Winterthurerstrasse 190, 8057 Zürich, Switzerland. verrey@access.unizh.ch
  • 2003-03-14
Published in:
  • Pflugers Archiv : European journal of physiology. - 2003
Amino Acid Transport System L
Amino Acid Transport System y+
Amino Acids, Neutral
Animals
Biological Transport
Epithelium
Fusion Regulatory Protein 1, Light Chains
Fusion Regulatory Protein-1
Humans
Intracellular Membranes
Large Neutral Amino Acid-Transporter 1
Osmolar Concentration
Tissue Distribution
English The plasma membrane transport system L is in many cells the only (efficient) pathway for the import of large branched and aromatic neutral amino acids. The corresponding transporters are hetero(di)mers composed of a catalytic subunit (LAT1 or LAT2=light chain=glycoprotein-associated amino acid transporter) associated covalently with the glycoprotein 4F2hc/CD98 (heavy chain). The tissue distribution of LAT1 suggests that it is involved mainly in transporting amino acids into growing cells and across some endothelial/epithelial secretory barriers, whereas the localization of LAT2 indicates that it is mainly involved in the basolateral efflux step of transepithelial (re)absorptive amino acid transport. However, system L transporters are obligatory amino acid exchangers with 1:1 stoichiometry, with similar (but not identical) intra- and extracellular substrate selectivities and with highly asymmetrical apparent affinities (low affinity inside). Therefore, net directional transport of large, neutral amino acids by system L depends on the parallel expression of a unidirectional transporter with overlapping selectivity (for instance systems A or N) that provides/recycles amino acids that drive system L exchange function. By mediating the regulated flux of these exchange substrates, unidirectional transporters control the activity of system L.
Language
  • English
Open access status
closed
Identifiers
Persistent URL
https://sonar.ch/global/documents/74932
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