A mutation in para-hydroxybenzoate-polyprenyl transferase (COQ2) causes primary coenzyme Q10 deficiency

Abstract

Ubiquinone (coenzyme Q(10) or CoQ(10)) is a lipid-soluble component of virtually all cell membranes, where it functions as a mobile electron and proton carrier. CoQ(10) deficiency is inherited as an autosomal recessive trait and has been associated with three main clinical phenotypes: a predominantly myopathic form with central nervous system involvement, an infantile encephalomyopathy with renal dysfunction, and an ataxic form with cerebellar atrophy. In two siblings of consanguineous parents with the infantile form of CoQ(10) deficiency, we identified a homozygous missense mutation in the COQ2 gene, which encodes para-hydroxybenzoate-polyprenyl transferase. The A-->G transition at nucleotide 890 changes a highly conserved tyrosine to cysteine at amino acid 297 within a predicted transmembrane domain. Radioisotope assays confirmed a severe defect of CoQ(10) biosynthesis in the fibroblasts of one patient. This mutation in COQ2 is the first molecular cause of primary CoQ(10) deficiency.

Figure 1

CoQ₁₀ biosynthetic pathway with eight known biosynthetic enzymes denoted as COQ1–COQ8. COQ2, decaprenyl-4-hydroxybenzoate transferase, mediates the conjugation of the benzoquinone ring with the decaprenyl side chain.

Figure 2

Evolutionary conservation of COQ2. Human amino acid 297 is normally tyrosine (Y). The A→G transition at nucleotide 890 changes amino acid 297 to cysteine.