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 COQ3, COQ4, COQ6, COQ7 and COQ9 polypeptides. Cofactor biosynthesis; ubiquinone biosynthesis. Component of a multi-subunit COQ enzyme complex, composed of at least COQ3, COQ4, COQ5, COQ6, COQ7 and COQ9. Interacts with COQ3. Belongs to the COQ4 family.