The X-Ray Structure of Zebrafish (Danio rerio) Ileal Bile Acid-Binding Protein Reveals the Presence of Binding Sites on the Surface of the Protein Molecule
Articolo
Data di Pubblicazione:
2009
Citazione:
The X-Ray Structure of Zebrafish (Danio rerio) Ileal Bile Acid-Binding Protein Reveals the Presence of Binding Sites on the Surface of the Protein Molecule / S. Capaldi, G. Saccomani, D. Fessas, M. Signorelli, M. Perduca, H.L. Monaco. - In: JOURNAL OF MOLECULAR BIOLOGY. - ISSN 0022-2836. - 385:1(2009), pp. 99-116.
Abstract:
The ileal bile acid-binding proteins (I-BABPs), also called ileal lipid-binding
proteins or gastrotropins, belong to the family of the fatty acid-binding
proteins and play an important role in the solubilization and transport of bile
acids in the enterocyte. This article describes the expression, purification,
crystallization, and three-dimensional structure determination of zebrafish
(Danio rerio) I-BABP both in its apo form and bound to cholic acid. This is the
first X-ray structure of an I-BABP. The structure of the apoprotein was
determined to a resolution of 1.6 Å, and two different monoclinic crystal
forms of the holoprotein were solved and refined to 2.2 Å resolution. Three
protein molecules are present in the asymmetric unit of one of the co-crystal
forms and two in the other, and therefore, the results of this study refer to
observations made on five different protein molecules in the crystalline state.
In every case, two cholate ligands were found bound in approximately the
same position in the internal cavity of the protein molecules, but an unexpected
result is the presence of clear and unambiguous electron density for
several cholate molecules bound on hydrophobic patches on the surface of
all the five independent protein molecules examined. Isothermal titration
calorimetry was used for the thermodynamic characterization of the binding
mechanism and has yielded results that are consistent with the X-ray data.
Ligand binding is described in detail, and the conformational changes
undergone by the protein molecule in the apo-to-holo transition are examined
by superposition of the apo- and holoprotein models. The structure of
the holoprotein is also compared with that of the liver BABP from the same
species and those of other I-BABPs determined by NMR.
Tipologia IRIS:
01 - Articolo su periodico
Elenco autori:
S. Capaldi, G. Saccomani, D. Fessas, M. Signorelli, M. Perduca, H.L. Monaco
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