PMID: 29414511

Authors:

Perduca M, Nicolis S, Mannucci B, Galliano M, Monaco HL

Title:

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

Journal:

Biochim Biophys Acta. 2018 Apr;1863(4):458-466. doi:, 10.1016/j.bbalip.2018.01.010.

Abstract:

RBP4 (plasma retinol-binding protein) is the 21kDa transporter of all-trans retinol that circulates in plasma as a moderately tight 1:1 molar complex of the vitamin with the protein. RBP4 is primarily synthesized in the liver but is also produced by adipose tissue and circulates bound to a larger protein, transthyretin, TTR, that serves to increase its molecular mass and thus avoid its elimination by glomerular filtration. This paper reports the high resolution three-dimensional structures of human RBP4 naturally lacking bound retinol purified from plasma, urine and amniotic fluid. In all these crystals we found a fatty acid molecule bound in the hydrophobic ligand-binding site, a result confirmed by mass spectrometry measurements. In addition we also report the 1.5A resolution structures of human holo-RBP4 and of the protein saturated with palmitic and lauric acid and discuss the interaction of the fatty acids and retinol with the protein.