1kqw
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Crystal structure of holo-CRBP from zebrafish
OverviewOverview
Cellular retinol-binding proteins (CRBPs) are cytoplasmic retinol-specific, binding proteins. Mammalian CRBPs have been thoroughly characterised, previously. Here we report on the identification and X-ray structural, analysis of the apo (1.7A resolution) and holo (1.4A resolution) forms of, a zebrafish CRBP. According to amino acid sequence and structure analyses, the zebrafish CRBP that we have identified resembles closely mammalian, CRBP II, suggesting that it is the zebrafish orthologue of this mammalian, CRBP type. Zebrafish CRBP forms a tight complex with all-trans retinol, producing an absorption spectrum similar to those of mammalian holo-CRBPs, albeit slightly blue-shifted. The superposition of the alpha-carbon atoms, of the liganded (complexed with retinol) and unliganded forms of zebrafish, CRBP shows significant differences in correspondence of the betaC-betaD, (residues 55-58) and betaE-betaF (residues 74-77) turns, providing, evidence for the occurrence of conformational changes accompanying retinol, binding/release. Remarkable and well-defined ligand-dependent, conformational changes in the protein region comprising the two beta-turns, affect both the main chain and the side-chains of several residues. The, two beta-turns project towards the interior of the cavity devoid of ligand, of the apoprotein. The side-chains of F57, Y60 and L77 change, substantially their orientation and position in the apoprotein relative to, the holoprotein. In the beta-barrel internal cavity of apo-CRBP they, occupy some of the space that is otherwise occupied by bound retinol in, holo-CRBP, and are displaced from these positions on ligand binding. These, results indicate that a flexible area encompassing the betaC-betaD and, betaE-betaF turns may serve as the ligand portal and that these turns, undergo conformational changes associated with the not yet clarified, mechanism of retinol binding and release in CRBPs.
About this StructureAbout this Structure
1KQW is a Single protein structure of sequence from Danio rerio with RTL as ligand. Full crystallographic information is available from OCA.
ReferenceReference
Identification and structural analysis of a zebrafish apo and holo cellular retinol-binding protein., Calderone V, Folli C, Marchesani A, Berni R, Zanotti G, J Mol Biol. 2002 Aug 16;321(3):527-35. PMID:12162964
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