Advanced

Serendipitous Fatty Acid Binding Reveals the Structural Determinants for Ligand Recognition in Apolipoprotein M

Sevvana, Madhumati; Ahnström, Josefin LU ; Egerer-Sieber, Claudia; Lange, Harald A.; Dahlbäck, Björn LU and Muller, Yves A. (2009) In Journal of Molecular Biology 393(4). p.920-936
Abstract
Apolipoprotein M (ApoM) is a 25-kDa HDL-associated apolipoprotein and a member of the lipocalin family of proteins. Mature apoM retains its signal peptide, which serves as a lipid anchor attaching apoM to the lipoproteins, thereby keeping it in the circulation. Studies in mice have suggested apoM to be antiatherogenic, but its physiological function is yet unknown. We have now determined the 1.95 angstrom resolution crystal structure of recombinant human apoM expressed in Escherichia coli and made the unexpected discovery that apoM, although refolded from inclusion bodies, was in complex with fatty acids containing 14, 16 or 18 carbon atoms. ApoM displays the typical lipocalin fold characterised by an eight-stranded antiparallel... (More)
Apolipoprotein M (ApoM) is a 25-kDa HDL-associated apolipoprotein and a member of the lipocalin family of proteins. Mature apoM retains its signal peptide, which serves as a lipid anchor attaching apoM to the lipoproteins, thereby keeping it in the circulation. Studies in mice have suggested apoM to be antiatherogenic, but its physiological function is yet unknown. We have now determined the 1.95 angstrom resolution crystal structure of recombinant human apoM expressed in Escherichia coli and made the unexpected discovery that apoM, although refolded from inclusion bodies, was in complex with fatty acids containing 14, 16 or 18 carbon atoms. ApoM displays the typical lipocalin fold characterised by an eight-stranded antiparallel beta-barrel that encloses an internal ligand-binding pocket. The crystal structures of two different complexes provide a detailed picture of the ligand-binding determinants of apoM. Additional fatty acid- and lipid-binding studies with apoM and the mutants apoM(W47F) and apoM(W100F) showed that sphingosine-1-phosphate is able to displace the bound fatty acids and efficiently quenched the intrinsic fluorescence with an IC50 of 0.90 mu M. Whereas the fatty acids bound in the crystal structure could be a mere consequence of recombinant protein production, the observed binding of sphingosine-l-phosphate might provide a key to a better understanding of the physiological function of apoM. (C) 2009 Elsevier Ltd. All rights reserved. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
lipocalin, binding, fatty acid, ligand-binding specificity, lipoproteins, crystal structure
in
Journal of Molecular Biology
volume
393
issue
4
pages
920 - 936
publisher
Elsevier
external identifiers
  • wos:000271528300011
  • scopus:70349813797
ISSN
1089-8638
DOI
10.1016/j.jmb.2009.08.071
language
English
LU publication?
yes
id
5da2688b-52fc-414a-9b7b-43d882f840be (old id 1520041)
date added to LUP
2009-12-28 10:45:36
date last changed
2017-08-13 04:04:02
@article{5da2688b-52fc-414a-9b7b-43d882f840be,
  abstract     = {Apolipoprotein M (ApoM) is a 25-kDa HDL-associated apolipoprotein and a member of the lipocalin family of proteins. Mature apoM retains its signal peptide, which serves as a lipid anchor attaching apoM to the lipoproteins, thereby keeping it in the circulation. Studies in mice have suggested apoM to be antiatherogenic, but its physiological function is yet unknown. We have now determined the 1.95 angstrom resolution crystal structure of recombinant human apoM expressed in Escherichia coli and made the unexpected discovery that apoM, although refolded from inclusion bodies, was in complex with fatty acids containing 14, 16 or 18 carbon atoms. ApoM displays the typical lipocalin fold characterised by an eight-stranded antiparallel beta-barrel that encloses an internal ligand-binding pocket. The crystal structures of two different complexes provide a detailed picture of the ligand-binding determinants of apoM. Additional fatty acid- and lipid-binding studies with apoM and the mutants apoM(W47F) and apoM(W100F) showed that sphingosine-1-phosphate is able to displace the bound fatty acids and efficiently quenched the intrinsic fluorescence with an IC50 of 0.90 mu M. Whereas the fatty acids bound in the crystal structure could be a mere consequence of recombinant protein production, the observed binding of sphingosine-l-phosphate might provide a key to a better understanding of the physiological function of apoM. (C) 2009 Elsevier Ltd. All rights reserved.},
  author       = {Sevvana, Madhumati and Ahnström, Josefin and Egerer-Sieber, Claudia and Lange, Harald A. and Dahlbäck, Björn and Muller, Yves A.},
  issn         = {1089-8638},
  keyword      = {lipocalin,binding,fatty acid,ligand-binding specificity,lipoproteins,crystal structure},
  language     = {eng},
  number       = {4},
  pages        = {920--936},
  publisher    = {Elsevier},
  series       = {Journal of Molecular Biology},
  title        = {Serendipitous Fatty Acid Binding Reveals the Structural Determinants for Ligand Recognition in Apolipoprotein M},
  url          = {http://dx.doi.org/10.1016/j.jmb.2009.08.071},
  volume       = {393},
  year         = {2009},
}