Alterations of the respiratory system of Neurospora crassa by the mi-1 mutation.

The respiratory mechanism of the cytochrome-defective mi-1 mutant of Neurospora crassa was partially characterized and compared with that of the wild type. Both systems of electron transport were linked to oxidative phosphorylation and showed similar characteristics with respect to substrates and components. The system operating in the cytochrome-deficient mi-1 mutant showed no characteristic alpha absorption bands of cytochromes a or b and was very unstable in vitro. The possibility that this system may be an altered form of the normal cytochrome electron transport chain which occurs in the wild type is discussed.