Flexibility is a likely determinant of binding specificity in the case of ileal lipid binding protein.
Lucke, C., Zhang, F., Ruterjans, H., Hamilton, J.A., Sacchettini, J.C.(1996) Structure 4: 785-800
- PubMed: 8805562 
- DOI: https://doi.org/10.1016/s0969-2126(96)00086-x
- Primary Citation of Related Structures:  
1EAL - PubMed Abstract: 
The family of lipid binding proteins (LBPs) includes a large number of fatty acid binding proteins (FABPs) but only two proteins (ileal lipid binding protein, ILBP, and liver fatty acid binding protein) that can bind both fatty acids and bile acids. Bile acid transport is medically and pharmacologically important, but is poorly understood. To understand the binding properties of ILBP, we studied its solution structure with and without bound lipids and compared these with known structures of FABPs.
Organizational Affiliation: 
Albert Einstein College of Medicine, Bronx, NY 10461, USA.