Uniporter that mediates the transport of extracellular choline and ethanolamine into cells, thereby playing a key role in phospholipid biosynthesis (PubMed:37100056, PubMed:38693265, PubMed:38778100, PubMed:39306721, PubMed:40972734). Choline and ethanolamine are the precursors of phosphatidylcholine and phosphatidylethanolamine, respectively, the two most abundant phospholipids (PubMed:38693265, PubMed:38778100). Transport is not coupled with proton transport and is exclusively driven by the choline (or ethanolamine) gradient across the plasma membrane (PubMed:38693265, PubMed:38778100). Also acts as a heme b transporter that mediates heme efflux from the cytoplasm to the extracellular compartment (PubMed:15369674, PubMed:20610401, PubMed:22483575, PubMed:23187127, PubMed:27923065). {ECO:0000269|PubMed:15369674, ECO:0000269|PubMed:20610401, ECO:0000269|PubMed:22483575, ECO:0000269|PubMed:23187127, ECO:0000269|PubMed:27923065, ECO:0000269|PubMed:37100056, ECO:0000269|PubMed:38693265, ECO:0000269|PubMed:38778100, ECO:0000269|PubMed:39306721}. [Isoform 1]: Uniporter that mediates the transport of extracellular choline and ethanolamine into cells (PubMed:37100056, PubMed:38693265). Choline and ethanolamine are the precursors of phosphatidylcholine and phosphatidylethanolamine, respectively, the two most abundant phospholipids (PubMed:38693265). Transport is not coupled with proton transport and is exclusively driven by the choline (or ethanolamine) gradient across the plasma membrane (PubMed:38693265). Also acts as a heme b transporter that mediates heme efflux from the cytoplasm to the extracellular compartment (PubMed:15369674, PubMed:20610401, PubMed:22483575, PubMed:23187127, PubMed:27923065). Heme export depends on the presence of HPX and is required to maintain intracellular free heme balance, protecting cells from heme toxicity (PubMed:20610401). Heme export provides protection from heme or ferrous iron toxicities in liver, brain, sensory neurons and during erythropoiesis, a process in which heme synthesis intensifies (PubMed:20610401, PubMed:23187127). Possibly export coproporphyrin and protoporphyrin IX, which are both intermediate products in the heme biosynthetic pathway (PubMed:20610401). Does not export bilirubin (PubMed:20610401). The molecular mechanism of heme transport, whether electrogenic, electroneutral or coupled to other ions, remains to be elucidated (PubMed:20610401, PubMed:23187127). {ECO:0000269|PubMed:15369674, ECO:0000269|PubMed:20610401, ECO:0000269|PubMed:22483575, ECO:0000269|PubMed:23187127, ECO:0000269|PubMed:27923065, ECO:0000269|PubMed:37100056, ECO:0000269|PubMed:38693265}. [Isoform 2]: Heme b transporter that promotes heme efflux from the mitochondrion to the cytoplasm. Essential for erythroid differentiation. . [Isoform 1]: (Microbial infection) Confers susceptibility to feline leukemia virus subgroup C (FeLV-C) infection in vitro. . This is the function of FLVCR1 (FLVCR choline and heme transporter 1, Ensembl gene identifier ENSG00000162769).