We have cloned the cDNA of a novel human ABC-half-transporter highly similar to peroxisomal ABC-half-transporters such as the adrenoleukodystrophy protein (ALDP) and the peroxisomal protein 70 (PMP70). This 2927-bp cDNA codes for a 606 aminoacid (68.6 kDa) protein that was designated PMP69 (putative peroxisomal membrane protein). PMP69 is ubiquitously expressed. Transcript variants resulting from alternative polyadenylation and splicing events including one that confers an alternative C-terminus have been found. The PMP69 gene is localized on chromosome 14q24.3. ABC-half-transporters require a partner ABC-half-transporter to constitute a functional complex, either as a homodimer or a heterodimer. Defects in the gene coding for ALDP are the cause of adrenoleukodystrophy, a demyelinating disorder of the nervous system with strikingly varying clinical courses. PMP70 was implicated in the pathogenesis of a subgroup of Zellweger syndrome, a heterogenous group of peroxisome assembly disorders. PMP69 might be a heterodimer partner for one of these proteins, thus playing a role in modifying the clinical course of ALD or, alternatively, in peroxisome biogenesis.

Three half ATP-binding cassette transporters (ALDP, ALDR, PMP70) are known to be present in the human peroxisome membrane. Mutations in the gene encoding ALDP cause X-linked adrenoleukodystrophy; the role of ALDR and PMP70 in human disease is unclear. We report the cloning and characterization of a fourth human gene encoding a peroxisomal half ABC transporter. The gene, designated P70R, maps to chromosome 14q24, encodes a 73 kDa transporter most similar to PMP70, and is expressed in all human tissues examined. Because half ABC transporters heterodimerize to form functional transporters, the identification of a fourth member of this family in the peroxisome membrane has implications for our understanding of mammalian peroxisomes and the genetic disorders of peroxisomal function.

>sp|O14678|ABCD4_HUMAN ATP-binding cassette sub-family D member 4 OS=Homo sapiens GN=ABCD4 PE=1 SV=1
MAVAGPAPGAGARPRLDLQFLQRFLQILKVLFPSWSSQNALMFLTLLCLTLLEQFVIYQVGLIPSQYYGVLGNKDLEGFK
TLTFLAVMLIVLNSTLKSFDQFTCNLLYVSWRKDLTEHLHRLYFRGRAYYTLNVLRDDIDNPDQRISQDVERFCRQLSSM
ASKLIISPFTLVYYTYQCFQSTGWLGPVSIFGYFILGTVVNKTLMGPIVMKLVHQEKLEGDFRFKHMQIRVNAEPAAFYR
AGHVEHMRTDRRLQRLLQTQRELMSKELWLYIGINTFDYLGSILSYVVIAIPIFSGVYGDLSPAELSTLVSKNAFVCIYL
ISCFTQLIDLSTTLSDVAGYTHRIGQLRETLLDMSLKSQDCEILGESEWGLDTPPGWPAAEPADTAFLLERVSISAPSSD
KPLIKDLSLKISEGQSLLITGNTGTGKTSLLRVLGGLWTSTRGSVQMLTDFGPHGVLFLPQKPFFTDGTLREQVIYPLKE
VYPDSGSADDERILRFLELAGLSNLVARTEGLDQQVDWNWYDVLSPGEMQRLSFARLFYLQPKYAVLDEATSALTEEVES
ELYRIGQQLGMTFISVGHRQSLEKFHSLVLKLCGGGRWELMRIKVE