Detection of suppressed maturation of the human COQ5 protein in the mitochondria following mitochondrial uncoupling by an antibody recognizing both precursor and mature forms of COQ5

Yeast Coq5p is required for the biosynthesis of coenzyme Q6 (CoQ6), but its human homolog has not been studied. We purified soluble recombinant human COQ5 protein under native conditions and generated an antibody recognizing both precursor and mature forms of COQ5. Mitochondrial localization of the mature form in 143B cells was demonstrated with this antibody. Moreover, a chemical uncoupler in a dose that suppressed CoQ10 levels downregulated the mature form but augmented the precursor form of COQ5. The results that knockdown of the COQ5 gene reduced CoQ10 levels further indicated the critical role of COQ5 in the biosynthesis of CoQ10.

► We developed an approach to purify the soluble recombinant human COQ5 protein. ► A self-made COQ5 antibody could recognize both precursor and mature forms of COQ5. ► Antibody specificity was verified by overexpression and knockdown of the COQ5 gene. ► FCCP that reduced CoQ10 levels suppressed COQ5 maturation in the mitochondria. ► Transient knockdown of the COQ5 gene reduced CoQ10 levels in human cells.