System L: heteromeric exchangers of large, neutral amino acids involved in directional transport.
Pflugers Arch
; 445(5): 529-33, 2003 Feb.
Article
en En
| MEDLINE
| ID: mdl-12634921
ABSTRACT
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 11 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.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Aminoácidos Neutros
/
Sistema de Transporte de Aminoácidos y/
/
Sistema de Transporte de Aminoácidos L
Límite:
Animals
/
Humans
Idioma:
En
Revista:
Pflugers Arch
Año:
2003
Tipo del documento:
Article
País de afiliación:
Suiza