Nature and transcriptional role of catalytic subunits of yeast mitochondrial cAMP-dependent protein kinase.

We have shown that mitochondrial (mt) transcription in yeast (S. cerevisiae) is governed in part by cAMP via a mt cAMP-dependent protein kinase (cAPK), and that the BCY1 gene product acts as regulatory subunit for that organellar enzyme, as it does for cytoplasmic cAPK. Here we assess mt cAPK activity and mt transcription in mutants for the TPK1, TPK2, and TPK3 genes, which encode catalytic subunits of cytoplasmic cAPK. Protein extracts from purified mitochondria from each of the three possible double TPK mutants show mt cAMP-dependent protein phosphorylation. Relative mt transcript levels in these mutants, however, suggest that TPK2 functions less well than does TPK1 or TPK3 in organellar transcriptional control. Thus, both mt and cytoplasmic cAPKs employ the same species of regulatory and catalytic proteins, and versions of the enzyme having various combinations of catalytic species function differentially in cAMP-dependent mt transcriptional control.