Autosomal recessive tetralogy of Fallot, unusual facies, communicating hydrocephalus, and delayed language development: a new syndrome?

We report a pattern of malformation affecting five of seven siblings born to unaffected Afghani parents who are first cousins. Their first two children died during infancy of cyanotic congenital heart defects. Two living male siblings have tetralogy of Fallot, developmental delay principally affecting language skills, and short palpebral fissures or midfacial hypoplasia. Another male has communicating hydrocephalus and hypertelorism. The striking number of siblings with tetralogy of Fallot, or another cyanotic congenital heart defect, and the parental consanguinity, suggests autosomal recessive inheritance in this family. While several other families have been identified with apparent recessive inheritance of tetralogy of Fallot, the associated malformations in our family suggest a unique, and previously unreported, malformation pattern.

Effect of membrane potential and pH gradient on electron transfer in cytochrome oxidase.

Steady-state spectra of cytochrome oxidase in phospholipid vesicles were obtained by using hexaammineruthenium(II) and ascorbate as reductants. Cytochrome a was up to 80% reduced in the steady state in coupled vesicles. Upon addition of nigericin or acetate, which decrease delta pH, resulting in an increase in delta psi, cytochrome a became more oxidized in the steady state with no change in the rate of respiration. On the other hand, uncouplers or valinomycin plus nigericin, which lower both delta psi and delta pH, stimulated respiration 2-8-fold and also lowered the steady-state level of reduction of cytochrome a. These experiments indicate that electron transfer between cytochromes a and a 3 is sensitive primarily to the pH gradient. Studies with the reconstituted and the soluble enzyme at various pH values indicated that the pH on the matrix side of the membrane, rather than delta pH, controlled the steady-state level of reduced cytochrome a. Hexaammineruthenium(II) substituted for cytochrome c in measurements of proton pumping by cytochrome oxidase. Dicyclohexylcarbodiimide, which eliminated proton pumping by cytochrome oxidase, decreased the effect of ionophores on the steady-state level of reduced cytochrome a.

Energetics of ATP-driven reverse electron transfer from cytochrome c to fumarate and from succinate to NAD in submitochondrial particles.

The maximum Gibbs free energies of reverse electron transfer from succinate to NAD+ and from cytochrome c to fumarate driven by ATP hydrolysis in submitochondrial particles from beef heart were measured as a function of the Gibbs free energy of ATP hydrolysis. The ratio of the energies delta G'redox/delta G'ATP was 1.40 from succinate to NAD+ and 0.89 from cytochrome c to succinate. The ratio, equivalent to a thermodynamic P/2e-ratio, was dependent on whether the electrochemical proton gradient was primarily a membrane potential or a pH gradient for the cytochrome c to fumarate reaction. The results are consistent with H+/ATP = 3 for F1 ATPase, H+/2e- = 4 for NADH-CoQ reductase, and H+(matrix)/2e- = 2 for succinate-cytochrome c reductase.