SLC46A1 encodes a transmembrane proton-coupled folate transporter protein that facilitates the movement of folate and antifolate substrates across cell membranes optimally in acidic pH environments. This protein is also expressed in the brain and choroid plexus where it transports folates into the central nervous system. This protein further functions as a transmembrane heme transporter in duodenal enterocytes and, potentially, in other tissues like liver and kidney. Its localization to the apical membrane or cytoplasm of intestinal cells is modulated by dietary iron levels. Mutations in this gene cause the autosomal recessive HFM disease. HFM is characterized by folate deficiency due to reduced intestinal folate absorption and subsequent anemia, hypoimmunoglobulinemia, and recurrent infections.