Profilingof Yeast Saccharomyces cerevisiae MitochondrialAMPylome Reveals a Regulation of OXPHOS Coupling throughATP Synthase Subunit Delta

Protein adenylation (AMPylation) is a post-translational modification in which an adenosine monophosphate (AMP) group is covalently attached to target proteins by AMPylases using ATP as a donor. In metazoans, two conserved AMPylase families are known: FIC-domain proteins and SelO. The yeast Saccharomyces cerevisiae lacks a FIC-domain enzyme; its only known AMPylase is the mitochondrial SelO homologue, Fmp40, involved in redox signaling. We conducted the first comprehensive screen for AMPylated proteins in the mitochondrial proteome of S. cerevisiae analyzing both wild-type and fmp40Δ cells using quantitative mass spectrometry. We identified 124 AMPylated mitochondrial proteins in wild-type and 41 in fmp40Δ mitochondria, suggesting the existence of additional AMPylase(s) in yeast. Among the modified targets, seven ATP synthase subunits were AMPylated, many at sites also phosphorylated, underscoring complex PTM regulation of the enzyme. We demonstrated that substitutions of one such residue, serine 29 in the δ subunit (Atp16), to alanine or glutamic acid, altered ATP synthase activity and oxidative phosphorylation coupling under both fermentative and respiratory conditions. This regulation is crucial for maintaining mitochondrial membrane potential. Our study provides the first catalog of AMPylated mitochondrial proteins in yeast, establishing a foundation for future studies on mitochondrial AMPylation.