cDNA cloning and mRNA expression of the human adrenoleukodystrophy related protein (ALDRP), a peroxisomal ABC transporter

Abstract

We have cloned the cDNA containing the complete coding region of the human adrenoleukodystrophy related (ALDR) gene. The 2220-bp open reading frame encodes a 740-amino-acid polypeptide with a predicted molecular weight of 83.3 kDa. The human ALDR protein displays high similarity (62.8% identical amino acid residues) to the human adrenoleukodystrophy (ALD) gene. Analysis of ALDR expression revealed the presence of ALDR mRNA in a variety of human tissues, predominantly in brain and heart. This expression pattern is different from all other known peroxisomal ABC-transporters. Defects in the ALD gene are the primary cause of adrenoleukodystrophy, a demyelinating disorder of the central nervous system. The ALD protein (ALDP) and the ALDR gene product are peroxisomal membrane proteins belonging to the superfamily of transporters containing an ATP-binding cassette (ABC-transporters). All known peroxisomal ABC-transporters represent only one-half of a functional transporter. They are expected to form dimers either as a homodimer or as a heterodimer. ALDRP is a potential dimerization partner of ALDP or other peroxisomal ABC-transporters. The ALDR gene is a candidate for a modifier gene, accounting for the strikingly varying clinical courses of ALD observed even within a family.