Binds free fatty acids and their coenzyme A derivatives, bilirubin, and some other small molecules in the cytoplasm. May be involved in intracellular lipid transport. Binds one trans-parinaric acid molecule or two cis-parinaric acid molecules. Affinity for mono- and polyunsaturated fatty acids is higher than that for saturated ones. Affinity for fatty acid coenzyme A derivatives, lysophosphatidic acid, lysophospholipds, retinoids, bilirubin and bile salts is similar to or higher than that for fatty acids. Affinity for prostaglandins, peroxisomal proliferators, bezafibrate and clofibrate is moderate to low. Forms a beta-barrel structure that accommodates hydrophobic ligands in its interior. Belongs to the calycin superfamily. Fatty-acid binding protein (FABP) family.