Does Intrinsic Disorder in Proteins Favor Their Interaction with Lipids?

Abstract

Intrinsically disordered proteins (IDPs) are implicated in a range of human diseases, some of which are associated with the ability to bind to lipids. Although the presence of solvent-exposed hydrophobic regions in IDPs should favor their interactions with low-molecular-weight hydrophobic/amphiphilic compounds, this hypothesis has not been systematically explored as of yet. In this study, the analysis of the DisProt database with regard to the presence of lipid-binding IDPs (LBIDPs) reveals that they comprise, at least, 15% of DisProt entries. LBIDPs are classified into four groups by ligand type, functional categories, domain structure, and conformational state. 57% of LBIDPs are classified as ordered according to the CH-CDF analysis, and 70% of LBIDPs possess lengths of disordered regions below 50%. To investigate the lipid-binding properties of IDPs for which lipid binding is not reported, three proteins from different conformational groups are rationally selected. They all are shown to bind linoleic (LA) and oleic (OA) acids with capacities ranging from 9 to 34 LA/OA molecules per protein molecule. The association with LA/OA causes the formation of high-molecular-weight lipid-protein complexes. These findings suggest that lipid binding is common among IDPs, which can favor their involvement in lipid metabolism.