Required for the function of coenzyme Q in the respiratory chain. May serve as a chaperone or may be involved in the transport of Q6 from its site of synthesis to the catalytic sites of the respiratory complexes (By similarity). Interacts with coenzyme Q. Belongs to the COQ10 family. The gene for this protein is duplicated in strains AX3 and AX4. These strains contain a duplication of a segment of 750 kb of chromosome 2 compared to the corresponding sequence in strain AX2.