Effects of disrupting the 21 kDa subunit of complex I from Neurospora crassa

Abstract

We have cloned and inactivated in vivo, by repeat-induced point mutations, the nuclear gene encoding a 21 kDa subunit of complex I from Neurospora crassa. Mitochondria from the nuo21 mutant lack this specific protein but retain other subunits of complex I in approximately normal amounts. In addition, this mutant is able to assemble an almost intact enzyme. The electron transfer activities from NADH to artificial acceptors of mitochondrial membranes from nuo21 differ from those of the wild-type strain, suggesting that the absence of the 21 kDa polypeptide results in conformational changes in complex I. Nevertheless, complex I of nuo21 is able to perform NADH:ubiquinone reductase activity, as judged by the observation that the respiration of mutant mitochondria is sensitive to inhibition by rotenone. We discuss these findings in relation to the involvement of complex I in mitochondrial diseases.

The 29.9kDa Subunit of Mitochondrial Complex I is Involved in the Enzyme Active/De-active Transitions

“…Two of them were the null-mutants nuo21 26 and nuo21.3a 27 obtained by specific gene inactivation, that respectively lack the 21 kDa and 21.3a kDa subunits of the peripheral arm of complex I. The other two mutants were obtained by site-directed mutagenesis.…”