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Real-time Analyses of Retinol Transport by the Membrane Receptor of Plasma Retinol Binding Protein
14:32

Real-time Analyses of Retinol Transport by the Membrane Receptor of Plasma Retinol Binding Protein

Published on: January 28, 2013

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Human plasma retinol-binding protein (RBP4) is also a fatty acid-binding protein

Massimiliano Perduca1, Stefania Nicolis2, Barbara Mannucci3

  • 1Biocrystallography Laboratory, Department of Biotechnology, University of Verona, Ca Vignal 1, strada Le Grazie 15, 37134 Verona, Italy.

Biochimica Et Biophysica Acta. Molecular and Cell Biology of Lipids
|February 8, 2018
PubMed

Insights

Plasma retinol-binding protein (RBP4) transports vitamin A. Studies reveal fatty acids, not just retinol, bind to RBP4

Area of Science:

  • Biochemistry
  • Structural Biology
  • Molecular Biology

Background:

  • Plasma retinol-binding protein (RBP4) is a 21 kDa protein responsible for transporting all-trans retinol.
  • RBP4 is synthesized mainly in the liver and also in adipose tissue, circulating in plasma bound to transthyretin (TTR).

Purpose of the Study:

  • To determine the high-resolution three-dimensional structures of human RBP4.
  • To investigate the binding interactions of fatty acids and retinol within the RBP4 ligand-binding site.

Main Methods:

  • Purification of human RBP4 from plasma, urine, and amniotic fluid.
  • High-resolution X-ray crystallography to determine protein structures.
  • Mass spectrometry to confirm ligand binding.

Main Results:

  • Crystals of RBP4 lacking retinol consistently showed a bound fatty acid molecule in the hydrophobic ligand-binding site.
  • Structures of holo-RBP4 and RBP4 saturated with palmitic and lauric acid were determined at 1.5 Å resolution.
  • Interactions between fatty acids, retinol, and the RBP4 protein were analyzed.

Conclusions:

  • Fatty acids are found to bind to the RBP4 ligand-binding site, even in the absence of retinol.
  • Structural data provides insights into the binding mechanisms of both retinol and fatty acids to RBP4.

Keywords:
Fatty acidLipocalin, TTR, Transthyretin, formerly called prealbuminRBP4, Plasma retinol-binding proteinX-ray structure

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