SLC46A1

Proton-coupled folate symporter that mediates folate absorption using an H(+) gradient as a driving force. Involved in 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 acts as a lower-affinity, pH-independent heme carrier protein and constitutes the main importer of heme in the intestine. Imports heme in the retina and retinal pigment epithelium, in neurons of the hippocampus, in hepatocytes and in the renal epithelial cells. Hence, participates in the trafficking of heme and increases intracellular iron content..

Function from UniProtKB (Q96NT5), read 2026-09-23. CC BY 4.0.