COQ9 also known as ubiquinone biosynthesis protein COQ9. This locus represents a mitochondrial ubiquinone biosynthesis gene. This protein is likely necessary for biosynthesis of coenzyme Q10, as mutations at this locus have been associated with autosomal-recessive neonatal-onset primary coenzyme Q10 deficiency. Recombinant human COQ9, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.