Characterization Of Proteins Associated With The Coenzyme Q Biosynthetic Complex And Analyses Of Phosphorylated Coq Proteins In Yeast Mitochondria

Coenzyme Q (also termed ubiquinone or CoQ) is an electron carrier in the mitochondrial respiratory chain that functions as an essential component in energy metabolism and serves as a vital lipid soluble antioxidant. Patients with CoQ defects suffer from various health disorders, such as kidney disease, neurodegenerative diseases, ataxia, and cardiovascular complications. Additionally, aging has also been linked to decreased CoQ levels. Saccharomyces cerevisiae serves as an excellent model for studies on CoQ biosynthesis and function because it is both a simple model and is highly conserved with respect to human CoQ biosynthesis. In yeast, several of the eleven proteins (Coq1p‐Coq9p, Yah1p, and Arh1p) necessary for the biosynthesis of CoQ 6 have been shown to be associated in a high molecular mass complex that localizes in the inner mitochondrial membrane, and has been termed the 'CoQ‐synthome'. Here we identify other potential protein partners that co‐purify with several of the Coq polypeptides and appear to be required for efficient Q biosynthesis. We use co‐immunoprecipitation techniques, Western blotting, blue native PAGE, lipid analysis, yeast cell growth assays, phosphorylation enrichment, and liquid chromatography‐tandem mass spectrometry to identify novel associated proteins and phosphorylation modifications sites of the Coq polypeptides. Elucidating their biosynthetic role in regulatory processes, such as phosphorylation, will aid our understanding and treatment of multiple diseases caused by CoQ‐deficiencies and will provide novel insight regarding longevity and issues related to aging in humans.