CLONING AND CHROMOSOMAL MAPPING OF A NOVEL ABC TRANSPORTER GENE (HABC7), A CANDIDATE FOR X-LINKED SIDEROBLASTIC ANEMIA WITH SPINOCEREBELLARATAXIA

We isolated a novel human ATP-binding cassette (ABC) transporter cDNA, determined its nucleotide sequence, and designated it human ABC7 (hAB C7). The nucleotide sequence was highly homologous to the ATM1 gene in yeast, which encodes an ABC transporter (yAtm1p) located in the mitoc hondrial inner membrane. The deduced human product, a putative half-ty pe transporter, consists of 752 amino acids that are 48.9 % identical to those of yAtm1p. A computer-assisted protein structural and localiz ation analysis revealed that the mitochondrial targeting signal of yAt m1p is conserved in the N-terminal region of the primary sequence of t he hABC7 protein, and therefore this product is also likely to be loca ted in the mitochondrial inner membrane. The evidence strongly suggest s that the hABC7 gene is a counterpart of ATM1 and that its product is probably involved in heme transport. We mapped the hABC7 gene to chro mosome Xq13.1-q13.3 by fluorescence in-situ hybridization. As band Xq1 3 has been implicated in X-linked sideroblastic anemia with spinocereb ellar ataxia, hABC7 becomes a candidate gene for this heritable disord er.