On complex I and other NADH : Ubiquinone reductases of Neurospora crassa mitochondria

The mitochondrial complex I is the first component of the respiratory chain coupling electron transfer from NADH to ubiquinone to proton translocation across the inner membrane of the organelle. The enzyme from the fungus Neu rospora crassa is similar to that of other organisms in terms of protein an d prosthetic group composition, structure, and function. It contains a high number of polypeptide subunits of dual genetic origin. Most of its subunit s were cloned, including those binding redox groups. Extensive gene disrupt ion experiments were conducted, revealing many aspects of the structure, fu nction, and biogenesis of complex I. Complex I is essential for the sexual phase of the life cycle of N. crassa, but not for the asexual stage. In add ition to complex I, the fungal mitochondria contain at least three nonproto n-pumping alternative NAD(P)H dehydrogenases feeding electrons to the respi ratory chain from either matrix or cytosolic substrates.