An open reading frame homologous with genes of non-proton-pumping NADH dehydrogenases was identified in the genome of Neurospora crassa. The 57 kDa NADH:ubiquinone oxidoreductase acts as internal (alternative) respiratory NADH dehydrogenase (NDI1) in the fungal mitochondria. The precursor polypeptide includes a pre-sequence of 31 amino acids, and the mature enzyme comprises one FAD molecule as a prosthetic group. It catalyses specifically the oxidation of NADH. Western blot analysis of fungal mitochondria fractionated with digitonin indicated that the protein is located at the inner face of the inner membrane of the organelle (internal enzyme). The corresponding gene was inactivated by the generation of repeat-induced point mutations. The respiratory activity of mitochondria from the resulting null-mutant ndi1 is almost fully inhibited by rotenone, an inhibitor of the proton-pumping complex I, when matrix-generated NADH is used as substrate. Although no effects of the NDI1 defect on vegetative growth and sexual differentiation were observed, the germination of both sexual and asexual ndi1 mutant spores is significantly delayed. Crosses between the ndi1 mutant strain and complex I-deficient mutants yielded no viable double mutants. Our data indicate: (i) that NDI1 represents the sole internal alternative NADH dehydrogenase of Neurospora mitochondria; (ii) that NDI1 and complex I are functionally complementary to each other; and (iii) that NDI1 is specially needed during spore germination.
Research Article| May 01 2003
The internal alternative NADH dehydrogenase of Neurospora crassa mitochondria
Arnaldo VIDEIRA 1
∗Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre 823, 4150–180 Porto, Portugal
‡Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Rua do Campo Alegre 823, 4150–180 Porto, Portugal
1To whom correspondence should be addressed (e-mail firstname.lastname@example.org).
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Margarida DUARTE, Markus PETERS, Ulrich SCHULTE, Arnaldo VIDEIRA; The internal alternative NADH dehydrogenase of Neurospora crassa mitochondria. Biochem J 1 May 2003; 371 (3): 1005–1011. doi: https://doi.org/10.1042/bj20021374
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