UbiB proteins regulate cellular CoQ distribution in Saccharomyces cerevisiae

Beyond its role in mitochondrial bioenergetics, Coenzyme Q (CoQ, ubiquinone) serves as a key membrane-embedded antioxidant throughout the cell. However, how CoQ is mobilized from its site of synthesis on the inner mitochondrial membrane to other sites of action remains a longstanding mystery. Here, using a combination of Saccharomyces cerevisiae genetics, biochemical fractionation, and lipid profiling, we identify two highly conserved but poorly characterized mitochondrial proteins, Ypl109c (Cqd1) and Ylr253w (Cqd2), that reciprocally affect this process. Loss of Cqd1 skews cellular CoQ distribution away from mitochondria, resulting in markedly enhanced resistance to oxidative stress caused by exogenous polyunsaturated fatty acids, whereas loss of Cqd2 promotes the opposite effects. The activities of both proteins rely on their atypical kinase/ATPase domains, which they share with Coq8-an essential auxiliary protein for CoQ biosynthesis. Overall, our results reveal protein machinery central to CoQ trafficking in yeast and lend insights into the broader interplay between mitochondria and the rest of the cell. Coenzyme Q (CoQ) is a lipid made in the inner mitochondrial membrane with antioxidant roles throughout the cell, but regulation of its cellular distribution is unclear. Here the authors identify two proteins that have reciprocal CoQ trafficking functions to help coordinate CoQ localization in yeast.

Automated summary

The authors have identified two proteins, Ypl109c (Cqd1) and Ylr253w (Cqd2), with reciprocal CoQ trafficking functions in yeast, shedding light on the regulation of Coenzyme Q distribution in the cell. Loss of Cqd1 skews CoQ distribution away from mitochondria, while loss of Cqd2 promotes the opposite effect.