Mitochondrial NAD Kinase Pos5 Is Required for CoQ Biosynthesis in Yeasts

by Shogo Nishihara, Ikuhisa Nishida, Yasuhiro Matsuo, Tomohiro Kaino, Makoto Kawamukai Coenzyme Q (CoQ) is an essential component of the electron transport chain, and ten genes involved in CoQ biosynthesis have been identified in Schizosaccharomyces pombe . To gain further insight into CoQ biosynthesis, we screened the Bioneer gene-deletion library and found that the Δpos5 strain produced only 0.2-fold of the wild-type CoQ 10 level.

Pos5 shares homology with Saccharomyces cerevisiae Pos5 (ScPos5), a mitochondrial NADH (or NAD + ) kinase that generates NADPH (or NADP + ). Heterologous expression of ScPOS5 in the S.

pombe Δ pos5 strain recovered CoQ content to 0.9-fold of the wild-type level, indicating functional conservation of Pos5 between the two yeasts. Consistently, CoQ 6 level in ΔScpos5 was decreased to 0.2-fold of that in the wild-type strain.

The Δpos5 strain exhibited several phenotypes characteristic of CoQ-deficient S. pombe , including inability to grow on non-fermentable carbon sources, hypersensitivity to oxidative stress, and high sulfide production.

Among CoQ biosynthetic enzymes, Coq6 monooxygenase is thought to utilize NADPH.