Abstract: We previously constructed two Schizosaccahromyces pombe
ubiquinone-10 (or Coenzyme Q_{10}) less mutants, which are
either defective for decaprenyl diphosphate synthase or
p-hydroxybenzoate polyprenyl diphosphate transferase. To
further confirm the roles of ubiquinone in S. pombe, we examined the
phenotype of the abc1Sp (coq8Sp) mutant, which is highly speculated
to be defective in ubiquinone biosynthesis. We show here that the abc1Sp
defective strain did not produce UQ-10 and could not grow on minimal medium.
The abc1Sp-deficient strain required supplementation with antioxidants
such as cysteine or glutathione to grow on minimal medium. In support of the
antioxidant function of ubiquinone, the abc1Sp-deficient strain is
sensitive to H_{2}O_{2} and
Cu^{2+}. In addition, expression of the stress inducible
ctt1 gene was much induced in the ubiquinone less mutant than wild type.
Interestingly, we also found that the abc1-deficient strain as well as
other ubiquinone less mutants produced a significant amount of
H_{2}S, which suggests that oxidation of sulfide by
ubiquinone may be an important pathway for sulfur metabolism in S. pombe.
Thus, analysis of the phenotypes of S. pombe ubiquinone less mutants
clearly demonstrate that ubiquinone has multiple functions in the cell apart
from being an integral component of the electron transfer system.
