Identification and functional reconstitution of the yeast peroxisomal adenine nucleotide transporter

The requirement for small molecule transport systems across the peroxisomal membrane has previously been postulated, but not directly proven. Here we report the identification and functional reconstitution of Ant1p (Ypr128cp) , a peroxisomal transporter in the yeast Saccharomyces cerevisiae, which ha s the characteristic sequence features of the mitochondrial carrier family. Ant1p was found to be an integral protein of the peroxisomal membrane and expression of ANTI was oleic acid inducible. Targeting of Ant1p to peroxiso mes was dependent on Pex3p and Pex19p, two peroxins specifically required f or peroxisomal membrane protein insertion. Ant1p was essential for growth o n medium-chain fatty acids as the sole carbon source. Upon reconstitution o f the overexpressed and purified protein into liposomes, specific transport of adenine nucleotides could be demonstrated. Remarkably, both the substra te and inhibitor specificity differed from those of the mitochondrial ADP/A TP transporter. The physiological role of Ant1p in S.cerevisiae is probably to transport cytoplasmic ATP into the peroxisomal lumen in exchange for AM P generated in the activation of fatty acids.