The S. cerevisiae YPR011cp is a mitochondrial carrier of adenosine-5’-phosphosulfate and 3’-phospho-adenosine 5’-phosphosulfate

The S. cerevisiae YPR011c gene is located on chromosome 16 and encodes a protein of unknown function with a sequence containing the characteristic features of the mitochondrial carrier family (MCF). Until now YPR011c has been investigated only in microarray analysis of the genome-wide transcription profile of S. cerevisiae concerning YPR011c is available ([1]; website of Yeast Microarray Global Viewer (YMGV)). In the present study YPR011cp was overexpressed in Escherichia coli, purified and reconstituted into liposomes. Our results demonstrate that YPR011cp is a mitochondrial transporter for adenosine-5’-phosphosulfate (APS) and 3’-phospho-adenosine 5’-phosphosulfate (PAPS). Besides transporting APS and PAPS, recombinant and reconstituted YPR011cp also transports sulfate, phosphate, thiosulfate and pyrosulfate. YPR011cp functions almost exclusively by a counter-exchange mechanism; our transport measurements in the reconstituted system indicate that APS and PAPS may cross the mitochondrial membrane in both directions via YPR011cp in exchange with sulfate or phosphate. This is true only for APS, which is produced by the MET3p (ATP sulfurylase) that has a dual cellular localization: cytosolic and mitochondrial [2]. Having established the transport function in vitro, we investigated the physiological significance of YPR011cp in yeast cells. Upon a temperature shift from 30 to 45 °C, S. cerevisiae cells do not survive in the absence of APS and PAPS [3]. At 45°C using cells lacking YPR011c gene and other mutants we have demonstrated that both cytosolic and mitochondrial APS are crucial to support S. cerevisiae cell survival. In addition, our results strongly suggest that APS produced in mitochondria is transported from the mitochondrial matrix to the cytosol via YPR011cp under thermal stress conditions. Finally, the cellular quantification of methionine and total glutathione suggest that APS-mediated protection may be, at least in part, related to the synthesis of glutathione which is necessary for protecting cells at high temperatures [4] and for replenishing cells with sulfur metabolites. This is the first time that mitochondria are found involved in thermotolerance by mediating the transport of APS to the cytosol, which may be the basis of a signaling mechanism crucial for cell survival at higher temperatures. [1] H.C. Causton, et al. Mol. Biol. Cell 12 (2001) 323–337. [2] A. Sickmann, et al. Proc. Natl. Acad. Sci. U. S. A. 100 (2003) 13207–13212. [3] H. Jakubowski, E. Goldman, J. Bacteriol. 175 (1993) 5469–5476. [4] K. Sugiyama, et al., Biochem. J. 352 (2000) 71–78.