Lipid binding protein response to a bile acid library: a combined NMR and statistical approach

Primary bile acids, differing in hydroxylation pattern, are synthesized from cholesterol in the liver and, once formed, can undergo extensive enzyme‐catalysed glycine/taurine conjugation, giving rise to a complex mixture, the bile acid pool. Composition and concentration of the bile acid pool may be altered in diseases, posing a general question on the response of the carrier (bile acid binding protein) to the binding of ligands with different hydrophobic and steric profiles. A collection of NMR experiments (H/D exchange, HET‐SOFAST, ePHOGSY NOESY/ROESY and 15N relaxation measurements) was thus performed on apo and five different holo proteins, to monitor the binding pocket accessibility and dynamics. The ensemble of obtained data could be rationalized by a statistical approach, based on chemical shift covariance analysis, in terms of residue‐specific correlations and collective protein response to ligand binding. The results indicate that the same residues are influenced by diverse chemical stresses: ligand binding always induces silencing of motions at the protein portal with a concomitant conformational rearrangement of a network of residues, located at the protein anti‐portal region. This network of amino acids, which do not belong to the binding site, forms a contiguous surface, sensing the presence of the bound lipids, with a signalling role in switching protein–membrane interactions on and off.

Lipid binding protein response to a bile acid library: a combined NMR and statistical approach Journal Articles