Lipid transport protein in adipocytes. Binds both long chain fatty acids and retinoic acid. Delivers long-chain fatty acids and retinoic acid to their cognate receptors in the nucleus (By similarity). Has the highest binding affinity for linoleic acid and decreasing relative affinity for eicosapentaenoic acid (EPA), alpha-linolenic acid (ALA), docosahexaenoic acid (DHA), oleic acid, palmitic acid and stearic acid, respectively (PubMed:26206084). Monomer. Depending on the nature of the ligand, a conformation change exposes a nuclear localization motif and the protein is transported into the nucleus. Subject to constitutive nuclear export. Forms a beta-barrel structure that accommodates the hydrophobic ligand in its interior. Belongs to the calycin superfamily. Fatty-acid binding protein (FABP) family.