Proton-coupled folate transporter that mediates folate absorption using an H(+) gradient as a driving force . Catalyzes the intestinal absorption of folates at the brush-border membrane of the proximal jejunum, and the transport from blood to cerebrospinal fluid across the choroid plexus . Functions at acidic pH via alternate outward- and inward-open conformation states . Protonation of residues in the outward open state primes the protein for transport . Binding of folate promotes breaking of salt bridge network and subsequent closure of the extracellular gate, leading to the inward-open state and release of protons and folate . Also able to transport antifolate drugs, such as methotrexate and pemetrexed, which are established treatments for cancer and autoimmune diseases . Involved in FOLR1-mediated endocytosis by serving as a route of export of folates from acidified endosomes . Also

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