Transports folate across the inner membranes of mitochondria (PubMed:15140890, PubMed:29666258). Can also transport FAD across the mitochondrial inner membrane (By similarity). Embryonic lethal (PubMed:29666258). Induces morphological abnormalities of neural tube defects in the entire head region of developing mouse embryos (PubMed:29666258). Belongs to the mitochondrial carrier (TC 2.A.29) family.