Regulation of cytoplasmic and mitochondrial leucyl-transfer ribonucleic acid synthetases in Neurospora crassa.

The production of cytoplasmic leucyl-transfer ribonucleic acid synthetase activity was found to be reciprocally proportional to that of the corresponding mitochondrial enzyme during logarithmic growth of strains of Neurospora crassa with normal mitochondria. In the presence of cni-3 mutant mitochondria, production of mitochondrial enzyme activity was greatly increased whereas cytoplasmic enzyme production remained constant. The effect of cni-3 on the yield of the two enzyme activities indicated that the regulatory mechanism involved is a complicated one that cannot be accounted for by the relatively simple transcription competition model proposed previously.