Sideroflexin1 (Sfxn1), the prototype of a novel family of evolutionarily conserved proteins present in eukaryotes, has been found mutated in mice with siderocytic anemia. It is speculated that this protein facilitates the transport of a component required for iron utilization into mitochondrial. During the large-scale sequencing analysis of a human fetal brain cDNA library, we isolated a cDNA encoding a novel sideroflexin protein (SFXN4), which showed 59% identity and 71% similarity to mouse sideroflexin4. According to the search of the human genome database, SFXN4 gene is mapped to chromosome 10q25-26 and spans more than 24.7kb of the genomic DNA. It is 1428 base pair in length and the putative protein contains 305 amino acids with a conserved predicted five-transmembrane-domains structure. RT-PCR result shows that the SFXN4 gene is expressed in many tissues.