REVERSIBLE CONFORMATIONAL-CHANGES OF RAT-LIVER FATTY-ACID BINDING-PROTEIN FOLLOWING LIPID-BINDING - CIRCULAR DICHROIC AND NUCLEAR-MAGNETIC-RESONANCE ANALYSIS

Only a single isoform (pI 5.0) of multiple rat liver fatty acid binding protein (FABP) was isolated and used throughout this investigation. When the final FABP preparation was partly freed of fatty acids by a mild delipidation technique using Lipidex, the secondary and tertiary structures were significantly changed, as demonstrated by circular dichroism (CD) and one- and two-dimensional nuclear magnetic resonance (H-1-NMR) spectroscopy. By delipidation, the FABP's alpha-helix was significantly increased and the beta-sheet was in turn decreased. The structural properties of the delipidated FABP, however, could be restored to nearly the original condition by recombining fatty acids. The findings suggest that the weakly bound fatty acids are responsible for the functional capacity of the FABP by changing the protein conformation.