Regulation of mitochondrial cAMP-dependent protein kinase activity in yeast

We have shown that transcription of the yeast (S. cerevisiae) mitochondrial (mt) genome is cAMP-sensitive, via a mt cAMP-dependent protein kinase (cAPK). In relation to that work, we examined whether the BCY 1 gene product functions as regulatory subunit for mt cAPK, as it does for the cytoplasmic enzyme. We demonstrate that mt protein extracts from a bcy 1 strain show no cAPK activity, whereas similar extracts from an otherwise isochromosomal BCY 1 strain show high levels of such activity. Partial purification of mt cAPK from each strain confirms this difference. Photoaffinity labeling with 8-N3[32P]cAMP and highly-purified mt protein extracts from the BCY 1 strain identifies one cAMP-binding protein (M(r) approximately 47000), while similar mt extracts from the bcy 1 strain lack all cAMP-binding proteins. These data suggest that BCY 1 regulates yeast mt cAPK, and that inactivation of BCY 1 removes that mt activity from cAMP control.