CHARACTERIZATION AND ANALYSIS OF CONSERVED MOTIFS IN A PEROXISOMAL ATP-BINDING CASSETTE TRANSPORTER

The adrenoleukodystrophy protein (ALDP) and the 70-kDa peroxisomal mem brane protein are half ATP-binding cassette (ABC) transporters in the human peroxisome membrane, Both are implicated in genetic disorders of peroxisome biogenesis and function, Proteins homologous to ALDP and t he 70-kDa peroxisomal membrane protein have been discovered in other e ukaryotic organisms and form a growing group of peroxisomal half ABC t ransporters. Amino acid sequence alignment of these and other ABC tran sporters reveals several protein motifs that are highly conserved both in sequence and location. Here we characterize two of these, designat ed the EAA-like and the loop1 motifs. We study them by introducing mis sense mutations in Pxa1p, a Saccharomyces cerevisiae ortholog of ALDP, and show that both motifs are important for Pxa1p function. Interesti ngly, missense mutations in corresponding amino acids in ALDP cause ad renoleukodystrophy in humans. We conclude that these motifs are import ant for ABC trans porter function and that the yeast protein Pxa1p is a useful system for understanding the molecular basis of adrenoleukody strophy.