Identification of a fourth half ABC transporter in the human peroxisomal membrane

Three half ATP-binding cassette transporters (ALDP, ALDR, PMP70) are knownto be present in the human peroxisome membrane. Mutations in the geneencoding ALDP cause X-linked adrenoleukodystrophy; the role of ALDR andPMP70 in human disease is unclear. We report the cloning andcharacterization of a fourth human gene encoding a peroxisomal half ABCtransporter. The gene, designated P70R, maps to chromosome 14q24, encodes a73 kDa transporter most similar to PMP70, and is expressed in all humantissues examined. Because half ABC transporters heterodimerize to formfunctional transporters, the identification of a fourth member of thisfamily in the peroxisome membrane has implications for our understanding ofmammalian peroxisomes and the genetic disorders of peroxisomal function.