JBC, Vol. 250, Issue 15, 5852-5858, Aug, 1975
Regulation of mitochondrial membrane assembly in Neurospora crassa. Transient expression of a respiratory mutant phenotype
J. L. Klein, D. L. Edwards and S. Werner
Cultures of mutant cni-1, a chromosomal mutant of Neurospora crassa,
undergo a marked change in respiratory properties as the age of the culture
increases. Early log phase cultures have a high level of respiration that
is insensitive to inhibition by cyanide or antimycin A. Late log and
stationary phase cultures have reduced rates of respiration. A high
percentage of this respiration is inhibited by cyanide. Mitochondria from
early log phase cni-1 have an excess of cytochrome c and little or no
detectable cytochrome aa3. Mitochondria from late log and stationary phase
cultures have levels of c-, b-, and a-type cytochromes that are not
significantly different in concentration from those found in wild type
cells. The cytochrome aa3 content and the cytochrome oxidase activity of
cni-1 mitochondria increase 5- to 10-fold as the age of the culture
increases. Mitochondria from early log phase cells of cni-1 synthesize only
polypeptides of apparent molecular weights 7,000 to 10,000 and donot
synthesize any of the mitochondrial components of cytochrome oxidase.
Mitochondria from late log and stationary phase cells synthesize the normal
complement of mitochondrial translation products including the
mitochondrial components of cytochrome oxidase. The assembly of cytochrome
oxidase is likely due to the availability of the mitochondrially
synthesized components of the enzyme. The regulation of mitochondrial
translation in the cni-1 mutant is independent of the nutrient content of
the growth medium and is due to the accumulation or depletion of some
component within the cell.