REGULATION OF MITOCHONDRIAL CAMP-DEPENDENT PROTEIN-KINASE ACTIVITY INYEAST

We have shown that transcription of the yeast (S. cerevisiae) mitochon drial (mt) genome is cAMP-sensitive, via a mt cAMP-dependent protein k inase (cAPK). In relation to that work, we examined whether the BCY1 g ene product functions as regulatory subunit for mt cAPK, as it does fo r the cytoplasmic enzyme. We demonstrate that mt protein extracts from a bcy1 strain show no cAPK activity, whereas similar extracts from an otherwise isochromosomal BCY1 strain show high levels of such activit y. Partial purification of mt cAPK from each strain confirms this diff erence. Photoaffinity labeling with 8-N-3[P-32]cAMP and highly-purifie d mt protein extracts from the BCY1 strain identifies one cAMP-binding protein (M(r) approximate to 47000), while similar mt extracts from t he bcy1 strain lack all cAMP-binding proteins. These data suggest that BCY1 regulates yeast mt cAPK, and that inactivation of BCY1 removes t hat mt activity from cAMP control.