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Hydrophobic ligand binding properties of the human lipocalin apolipoprotein M

Ahnström, Josefin LU ; Faber, Kirsten LU ; Axler, Olof LU and Dahlbäck, Björn LU (2007) In Journal of Lipid Research 48(8). p.1754-1762
Abstract
Apolipoprotein M (apoM) is a plasma protein associated mainly with HDL. ApoM is suggested to be important for the formation of pre beta-HDL, but its mechanism of action is unknown. Homology modeling has suggested apoM to be a lipocalin. Lipocalins share a structurally conserved beta-barrel, which in many lipocalins bind hydrophobic ligands. The aim of this study was to test the ability of apoM to bind different hydrophobic substances. ApoM was produced both in Escherichia coli and in HEK 293 cells. Characterization of both variants with electrophoretic and immunological methods suggested apoM from E. coli to be correctly folded. Intrinsic tryptophan fluorescence of both apoM variants revealed that retinol, all-trans-retinoic acid, and... (More)
Apolipoprotein M (apoM) is a plasma protein associated mainly with HDL. ApoM is suggested to be important for the formation of pre beta-HDL, but its mechanism of action is unknown. Homology modeling has suggested apoM to be a lipocalin. Lipocalins share a structurally conserved beta-barrel, which in many lipocalins bind hydrophobic ligands. The aim of this study was to test the ability of apoM to bind different hydrophobic substances. ApoM was produced both in Escherichia coli and in HEK 293 cells. Characterization of both variants with electrophoretic and immunological methods suggested apoM from E. coli to be correctly folded. Intrinsic tryptophan fluorescence of both apoM variants revealed that retinol, all-trans-retinoic acid, and 9-cis-retinoic acid bound ( dissociation constant 5 2-3 mu M), whereas other tested substances ( e.g., cholesterol, vitamin K, and arachidonic acid) did not. The intrinsic fluorescence of two apoM mutants carrying single tryptophans was quenched by retinol and retinoic acid to the same extent as wild-type apoM, indicating that the environment of both tryptophans was affected by the binding. In conclusion, the binding of retinol and retinoic acid supports the hypothesis that apoM is a lipocalin. The physiological relevance of this binding has yet to be elucidated. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
cholesterol, signal peptide, lipoprotein, high density, intrinsic fluorescence, retinol, retinoic acid
in
Journal of Lipid Research
volume
48
issue
8
pages
1754 - 1762
publisher
American Society for Biochemistry and Molecular Biology
external identifiers
  • wos:000248044200010
  • scopus:34548149278
ISSN
1539-7262
DOI
10.1194/jlr.M700103-JLR200
language
English
LU publication?
yes
id
d6b5be0f-41d3-4236-b80e-39445ce5240e (old id 691672)
date added to LUP
2007-12-06 13:15:57
date last changed
2017-11-19 03:34:04
@article{d6b5be0f-41d3-4236-b80e-39445ce5240e,
  abstract     = {Apolipoprotein M (apoM) is a plasma protein associated mainly with HDL. ApoM is suggested to be important for the formation of pre beta-HDL, but its mechanism of action is unknown. Homology modeling has suggested apoM to be a lipocalin. Lipocalins share a structurally conserved beta-barrel, which in many lipocalins bind hydrophobic ligands. The aim of this study was to test the ability of apoM to bind different hydrophobic substances. ApoM was produced both in Escherichia coli and in HEK 293 cells. Characterization of both variants with electrophoretic and immunological methods suggested apoM from E. coli to be correctly folded. Intrinsic tryptophan fluorescence of both apoM variants revealed that retinol, all-trans-retinoic acid, and 9-cis-retinoic acid bound ( dissociation constant 5 2-3 mu M), whereas other tested substances ( e.g., cholesterol, vitamin K, and arachidonic acid) did not. The intrinsic fluorescence of two apoM mutants carrying single tryptophans was quenched by retinol and retinoic acid to the same extent as wild-type apoM, indicating that the environment of both tryptophans was affected by the binding. In conclusion, the binding of retinol and retinoic acid supports the hypothesis that apoM is a lipocalin. The physiological relevance of this binding has yet to be elucidated.},
  author       = {Ahnström, Josefin and Faber, Kirsten and Axler, Olof and Dahlbäck, Björn},
  issn         = {1539-7262},
  keyword      = {cholesterol,signal peptide,lipoprotein,high density,intrinsic fluorescence,retinol,retinoic acid},
  language     = {eng},
  number       = {8},
  pages        = {1754--1762},
  publisher    = {American Society for Biochemistry and Molecular Biology},
  series       = {Journal of Lipid Research},
  title        = {Hydrophobic ligand binding properties of the human lipocalin apolipoprotein M},
  url          = {http://dx.doi.org/10.1194/jlr.M700103-JLR200},
  volume       = {48},
  year         = {2007},
}