NDUFA10

Abstract: Complex I (NADH:ubiquinone oxidoreductase) uses the reducing potential of NADH to drive protons across the energy-transducing inner membrane and power oxidative phosphorylation in mammalian mitochondria. Recent cryo-EM analyses have produced near-complete models of all 45 subunits in the bovine, ovine and porcine complexes and have identified two states relevant to complex I in ischemia-reperfusion injury. Here, we describe the 3.3-A structure of complex I from mouse heart mitochondria, a biomedically relevant model system, in the 'active' state. We reveal a nucleotide bound in subunit NDUFA10, a nucleoside kinase homolog, and define mechanistically critical elements in the mammalian enzyme. By comparisons with a 3.9-A structure of the 'deactive' state and with known bacterial structures, we identify differences in helical geometry in the membrane domain that occur upon activation or that alter the positions of catalytically important charged residues. Our results demonstrate the capability of cryo-EM analyses to challenge and develop mechanistic models for mammalian complex I.

Abstract: Mitochondrial complex I deficiency is the most common defect of the oxidative phosphorylation system. We report a patient with Leigh syndrome who showed a complex I deficiency expressed in cultured fibroblasts and muscle tissue. To find the genetic cause of the complex I deficiency, we screened the mitochondrial DNA and the nuclear-encoded subunits of complex I. We identified compound-heterozygous mutations in the NDUFA10 gene, encoding an accessory subunit of complex I. The first mutation disrupted the start codon and the second mutation resulted in an amino acid substitution. The fibroblasts of the patient displayed decreased amount and activity, and a disturbed assembly of complex I. These results indicate that NDUFA10 is a novel candidate gene to screen for disease-causing mutations in patients with complex I deficiency.