Component of the coenzyme Q biosynthetic pathway. May play a role in organizing a multi-subunit COQ enzyme complex required for coenzyme Q biosynthesis. Required for steady-state levels of other COQ polypeptides. Cofactor biosynthesis; ubiquinone biosynthesis. Component of a multi-subunit COQ enzyme complex, composed of at least coq-3, coq-4, coq-5, coq-6, coq-7 and coq-9. Belongs to the COQ4 family.