Atypical kinase involved in the biosynthesis of coenzyme Q, also named ubiquinone, an essential lipid-soluble electron transporter for aerobic cellular respiration (PubMed:27499294). Affects the molecular organization and function of COQ3, possibly through kinase activity towards COQ3, COQ5 and/or COQ7 (PubMed:11279158, PubMed:15063807, PubMed:1648478, PubMed:18801050, PubMed:19002377, PubMed:21296186, PubMed:9210471, PubMed:9266513, PubMed:25498144). Its substrate specificity is unclear: does not show any protein kinase activity (PubMed:27499294). Probably acts as a small molecule kinase, possibly a lipid kinase that phosphorylates a prenyl lipid in the ubiquinone biosynthesis pathway, as suggested by its ability to bind coenzyme Q lipid intermediates (By similarity). Cofactor biosynthesis; ubiquinone biosynthesis. Forms homopolymers. Predominantly associated with a complex of about 500 kDa. Adopts an atypical protein kinase-like fold: while it adopts a core fold similar to that of well-characterized protein kinase-like domains. The KxGQ motif completely occludes the typical substrate binding pocket. Nucleotide-binding opens the substrate binding pocket and flips the active site from inside the hydrophobic core into a catalytically competent, solvent-exposed posture. Decreases COQ3 O-methyltransferase activity. Present with 952 molecules/cell in log phase SD medium. Belongs to the protein kinase superfamily. ADCK protein kinase family. Able to autophosphorylate in cis in vitro. This activity may not be relevant in vivo and only reflects in vitro conditions. Probably does not act as a protein kinase as it is unable to act in trans (PubMed:27499294). Was originally (PubMed:1648478) isolated as a multicopy suppressor of a yeast strain harboring a mutation in a cytochrome b translational activator (cbs2-223). But more recently it has been shown (PubMed:15063807) that a tRNA(Trp) gene located downstream of COQ8 mediates suppression of the cbs2-223 mutation. The inability of COQ8 to suppress the cbs2-223 allele in multicopy indicates it may not be a chaperone as previously reported.