IDENTIFICATION OF THE YEAST ACR1 GENE-PRODUCT AS A SUCCINATE-FUMARATETRANSPORTER ESSENTIAL FOR GROWTH ON ETHANOL OR ACETATE

The protein encoded by the ACR1 gene in Saccharomyces cerevisiae belon gs to a family of 35 related membrane proteins that are encoded in the fungal genome. Some of them are known to transport various substrates and products across the inner membranes of mitochondria, but the func tions of 28 members of the family are unknown. The yeast ACR1 gene was introduced into Escherichia coli on an expression plasmid. The protei n was over-produced as inclusion bodies, which were purified and solub ilised in the presence of sarkosyl. The solubilised protein was recons tituted into liposomes and shown to transport fumarate and succinate. Its physiological role in S. cerevisiae is probably to transport cytop lasmic succinate, derived from isocitrate by the action of isocitrate lyase in the cytosol, into the mitochondrial matrix in exchange for fu marate. This exchange activity and the subsequent conversion of fumara te to oxaloacetate in the cytosol would be essential for the growth of S. cerevisiae on ethanol or acetate as the sole carbon source. (C) 19 97 Federation of European Biochemical Societies.