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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
Summary
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.
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