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Identification of the retinol‐binding protein (RBP) interaction site and functional state of RBPs for the membrane receptor
Author(s) -
Redondo Clara,
Vouropoulou Maria,
Evans Jonathan,
Findlay John B. C.
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.07-8939com
Subject(s) - retinol binding protein , retinol , receptor , binding site , biochemistry , transport protein , microbiology and biotechnology , chemistry , membrane protein , ligand (biochemistry) , transmembrane protein , biophysics , membrane , biology , vitamin
This laboratory has advanced a model whereby retinol is transported around the body bound to retinol‐binding protein (RBP), is transferred across the membrane of cells by a specific receptor/transporter, and is picked up from the membrane by an intracellular homolog, cellular retinol‐binding protein (CRBP). This process involves a number of proteinprotein interactions, and we hypothesized that confor‐mational changes were an integral part of the retinol transfer mechanism. Previously we identified the potential interaction site on RBP for its membrane receptor. Here we confirm by the analysis of chimera containing a grafted CD loop from RBP that this is indeed the receptor interaction site and go on to demonstrate that the conformational changes that occur to this region on the apo to holo transition in RBP also take place in a chimera binding a quite different ligand, thus establishing the concept. We have also gone on to support the hypothesis that CRBP may also bind to a receptor in the membrane. Previous evidence has indicated that one such receptor might be lecithin:retinol acyltransferase, an enzyme that catalyzes retinol esterification. Here we provide the first evidence that the plasma membrane receptor for RBP could be the same as that for CRBP. This observation offers support for the intracellular phase of the uptake process for retinol, providing an efficient and highly unique mechanism in eukaryotic biology. Redondo, C., Vouropoulou, M., Evans, J., Findlay, J. B. C. Identification of the retinol‐binding protein (RBP) interaction site and functional state of RBPs for the membrane receptor. FASEB J. 22, 1043–1054 (2008)