Heterodimeric amino acid transporters are comprised of a type-II membrane protein named the heavy chain (4F2hc or rBAT) that may associate with a number of different polytopic membrane proteins, called light chains. It is thought that the heavy chain is mainly involved in the trafficking of the complex to the plasma membrane, whereas the transport process itself is catalysed by the light chain. The 4F2heavy chain (4F2hc) associates with at least six different light chains to induce distinct amino acid-transport activites. To test if the light chains are specifically recognized and to identify domains involved in the recognition of light chains, C-terminally truncated mutants of 4F2hc were constructed and co-expressed with the light chains LAT1, LAT2 and y+LAT2. The truncated isoform T1, comprised of only 133 amino acids that form the cytosolic N-terminus and the transmembrane helix, displayed only a slight reduction in its ability to promote LAT1 expression at the membrane surface compared with the 529 amino acid wild-type 4F2hc protein. Co-expression of increasingly larger 4F2hc mutants caused a delayed translocation of LAT1. In contrast to the weak effects of 4F2hc truncations on LAT1 expression, surface expression of LAT2 and y+LAT2 was almost completely lost with all truncated heavy chains. Co-expression of LAT1 together with the other light chains did not result in displacement of LAT2 and y+LAT2. The results suggest that extracellular domains of the heavy chain are responsible mainly for recognition of light chains other than LAT1 and that the extracellular domain ensures proper translocation to the plasma membrane.
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Research Article|
April 24 2001
Association of 4F2hc with light chains LAT1, LAT2 or y+LAT2 requires different domains
Angelika BRÖER;
Angelika BRÖER
*Division of Biochemistry & Molecular Biology, Faculty of Science, Australian National University, Canberra, ACT 0200, Australia,
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Björn FRIEDRICH;
Björn FRIEDRICH
†Department of Physiology, University of Tübingen, Gmelinstr. 5, D-72076 Tübingen, Germany,
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Carsten A. WAGNER;
Carsten A. WAGNER
‡Department of Cellular and Molecular Physiology, School of Medicine, Yale University, New Haven, CT 06520, U.S.A.
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Sophie FILLON;
Sophie FILLON
†Department of Physiology, University of Tübingen, Gmelinstr. 5, D-72076 Tübingen, Germany,
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Vadivel GANAPATHY;
Vadivel GANAPATHY
§Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, U.S.A.
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Florian LANG;
Florian LANG
†Department of Physiology, University of Tübingen, Gmelinstr. 5, D-72076 Tübingen, Germany,
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Stefan BRÖER
Stefan BRÖER
1
*Division of Biochemistry & Molecular Biology, Faculty of Science, Australian National University, Canberra, ACT 0200, Australia,
1To whom correspondence should be addressed (e-mail stefan.broeer@anu.edu.au).
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Publisher: Portland Press Ltd
Received:
November 15 2000
Revision Received:
January 24 2001
Accepted:
February 19 2001
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 2001
2001
Biochem J (2001) 355 (3): 725–731.
Article history
Received:
November 15 2000
Revision Received:
January 24 2001
Accepted:
February 19 2001
Citation
Angelika BRÖER, Björn FRIEDRICH, Carsten A. WAGNER, Sophie FILLON, Vadivel GANAPATHY, Florian LANG, Stefan BRÖER; Association of 4F2hc with light chains LAT1, LAT2 or y+LAT2 requires different domains. Biochem J 1 May 2001; 355 (3): 725–731. doi: https://doi.org/10.1042/bj3550725
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