ANALYSIS OF THE DECAPRENYL DIPHOSPHATE SYNTHASE (DPS) GENE IN FISSIONYEAST SUGGESTS A ROLE OF UBIQUINONE AS AN ANTIOXIDANT

Schizosaccharomyces pombe produces ubiquinone-10 whose side chain is t hought to be provided by the product generated by decaprenyl diphospha te synthase, To understand the mechanism of ubiquinone biosynthesis in S. pombe, we have cloned the gene encoding decaprenyl diphosphate syn thase by the combination of PCR amplification of the fragment and subs equent library screening, The determined DNA sequence of the cloned ge ne, called dps, revealed that the dps gene encodes a 378-amino-acid pr otein that has the typical conserved regions observed in many polypren yl diphosphate synthases, Computer-assisted homology search indicated that Dps is 45 and 33% identical with hexaprenyl diphosphate synthase from Saccharomyces cerevisiae and octaprenyl diphosphate synthase from Escherichia coli, respectively, An S. pombe dps-deficient strain was constructed, This disruptant was not able to synthesize ubiquinone and had no detectable decaprenyl diphosphate synthase activity, indicatin g that the dps gene is unique and responsible for ubiquinone biosynthe sis, The S. pombe dps-deficient strain could not grow on either rich m edium supplemented with glycerol or on minimal medium supplemented wit h glucose, The dps-deficient strain required cysteine or glutathione f or full growth on the minimal medium, In addition, the dps-deficient s train is more sensitive to H2O2 and Cu2+ than the wild type, These res ults suggests a role of ubiquinone as an antioxidant in fission yeast cells.