H+-slip correlated to rotor free-wheeling as cause of F1FO-ATPase dysfunction in primary mitochondrial disorders

Abstract

Inborn errors of metabolism are related to mitochondrial disorders caused by dysfunction of the oxidative phosphorylation (OXPHOS) system. Congenital hypermetabolism in the infant is a rare disease belonging to Luft syndrome, nonthyroidal hypermetabolism, arising from a singular example of a defect in OXPHOS. The mitochondria lose coupling of mitochondrial substrates oxidation from the ADP phosphorylation. Since Luft syndrome is due to uncoupled cell respiration responsible for deficient in ATP production that originates in the respiratory complexes, a de novo heterozygous variant in the catalytic subunit of mitochondrial F₁F_O-ATPase arises as the main cause of an autosomal dominant syndrome of hypermetabolism associated with dysfunction in ATP production, which does not involve the respiratory complexes. The F₁F_O-ATPase works as an embedded molecular machine with a rotary action using two different motor engines. The F_O, which is an integral domain in the membrane, dissipates the chemical potential difference for H⁺, a proton motive force (Δp), across the inner membrane to generate a torsion. The F₁ domain-the hydrophilic portion responsible for ATP turnover-is powered by the molecular rotary action to synthesize ATP. The structural and functional coupling of F₁ and F_O domains support the energy transduction for ATP synthesis. The dissipation of Δp by means of an H⁺ slip correlated to rotor free-wheeling of the F₁F_O-ATPase has been discovered to cause enzyme dysfunction in primary mitochondrial disorders. In this insight, we try to offer commentary and analysis of the molecular mechanism in these impaired mitochondria.

Keywords: ATP synthase; bioenergetic failure; congenital hypermetabolism; de novo mutation; mitochondria.