Binds and may transport fatty acids such as palmitoleate (PubMed:22948910). Also binds poly-phosphoinositides including phosphatidylinositol 4-phosphate (PtdIns(4)P), phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) and phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3), and phosphatidic acid (PubMed:19168028). When phosphorylated, stimulates the activity of optic nerve Na(+)/Ca(2+) exchanger (PubMed:19168028, PubMed:19386360, PubMed:22948910). Interacts with Na(+)/Ca(2+) exchanger NCXSQ1; ReP1-NCXSQ phosphorylation does not affect the interaction. Expressed in the optic nerve (at protein level). Forms a beta-barrel structure that accommodates hydrophobic ligands in its interior. Phosphorylated (PubMed:19168028, PubMed:23224877, PubMed:19386360). Phosphorylation may result in the release of the bound fatty acid (PubMed:22948910). Belongs to the calycin superfamily. Fatty-acid binding protein (FABP) family.