A conserved START domain coenzyme Q-binding polypeptide is required for efficient Q biosynthesis, respiratory electron transport, and antioxidant function in Saccharomyces cerevisiae

Abstract

Coenzyme Qn (ubiquinone or Qn) is a redox active lipid composed of a fully substituted benzoquinone ring and a polyisoprenoid tail of n isoprene units. Saccharomyces cerevisiae coq1-coq9 mutants have defects in Q biosynthesis, lack Q6, are respiratory defective, and sensitive to stress imposed by polyunsaturated fatty acids. The hallmark phenotype of the Q-less yeast coq mutants is that respiration in isolated mitochondria can be rescued by the addition of Q2, a soluble Q analog. Yeast coq10 mutants share each of these phenotypes, with the surprising exception that they continue to produce Q6. Structure determination of the Caulobacter crescentus Coq10 homolog (CC1736) revealed a steroidogenic acute regulatory protein-related lipid transfer (START) domain, a hydrophobic tunnel known to bind specific lipids in other START domain family members. Here we show that purified CC1736 binds Q2, Q3, Q10, or demethoxy-Q3 in an equimolar ratio, but fails to bind 3-farnesyl-4-hydroxybenzoic acid, a farnesylated analog of an early Q-intermediate. Over-expression of C. crescentus CC1736 or COQ8 restores respiratory electron transport and antioxidant function of Q6 in the yeast coq10 null mutant. Studies with stable isotope ring precursors of Q reveal that early Q-biosynthetic intermediates accumulate in the coq10 mutant and de novo Q-biosynthesis is less efficient than in the wild-type yeast or rescued coq10 mutant. The results suggest that the Coq10 polypeptide:Q (protein:ligand) complex may serve essential functions in facilitating de novo Q biosynthesis and in delivering newly synthesized Q to one or more complexes of the respiratory electron transport chain.

Identification of Coq11, a New Coenzyme Q Biosynthetic Protein in the CoQ-Synthome in Saccharomyces cerevisiae

“…The ability of the ylr290c⌬ mutant to grow on a nonfermentable carbon source despite its decreased Q synthesis is not surprising, because other mutants with decreased Q synthesis have been characterized and retain the ability to grow on a nonfermentable carbon source. The coq10⌬ mutant and particular yeast coq5 mutants expressing human COQ5 retain the ability to grow on a nonfermentable carbon source despite having significantly decreased Q synthesis (56,57). However, the ylr290c⌬ mutant appeared to synthesize wild-type levels of Q 6 when grown in rich medium.…”

“…Such fusion proteins, also known as Rosetta Stone proteins, are often indicative of a functional link between two proteins including a physical interaction or residency in the same pathway (73). Coq10 was shown to be required for efficient de novo Q biosynthesis (56), and several studies indicate that yeast Coq10 and orthologs bind Q or DMQ via a hydrophobic START domain (56,74,75), leading to the hypothesis that Coq10 acts a Q chaperone, necessary for delivery of Q to the CoQ-synthome for efficient de novo Q synthesis and respiration (56). The fusion of YLR290C with Coq10 strongly suggests a functional interaction of YLR290C with this Q-binding protein.…”

Resveratrol and para-coumarate serve as ring precursors for coenzyme Q biosynthesis

“…The in vivo metabolism of potential ring precursors labeled with the stable isotope 13 C can be determined with high sensitivity and specifi city with reverse phase (RP)-HPLC-MS/MS identifi cation and quantifi cation. Using this approach, Block et al ( 15 ) showed that Arabidopsis was not able to incorporate 13 C 6 -pABA into Q.…”

“…13 C NMR spectral data are reported in terms of chemical shift ( ␦ , parts per million), multiplicity, and coupling constant (hertz …”

Coenzyme Q supplementation or Over-Expression of the Yeast Coq8 Putative Kinase Stabilizes Multi-Subunit Coq Polypeptide Complexes in Yeast Coq Null Mutants

“…Recent evidence suggests that the interaction between the Coq10 polypeptide and Q is essential for the function of Q in respiration and for efficient de novo synthesis of Q [37][38][39]. Respiration in mitochondria isolated from yeast coq10 mutants can be rescued by the addition of Q 2 , a soluble analog of Q 6 .…”