Structural Superimposition

Abstact

Acetyl-coenzyme A synthetases convert ATP, acetate, and coenzyme A (CoA) into acetyl-CoA, a central metabolite that fuels lipid biosynthesis and regulates protein and RNA acetylation. ACS enzymes contain N- and C-terminal domains that coordinate a two-step ping-pong mechanism involving sequential adenylation and thioester formation at the interdomain interface. How domain motions coordinate these chemical steps remains unclear. Here, we report single-particle cryo-electron microscopy structures of Schizosaccharomyces pombe ACSA captured in apo, pre-adenylation, intermediate, and product states. These structures reveal ligand-dependent reorganization of the C-terminal domain: apo and pre-adenylation forms display increased conformational heterogeneity, whereas intermediate- and product-bound states adopt ordered conformations compatible with catalysis. Structure-guided mutagenesis and in vitro activity assays, together with sequence conservation, support the functional importance and evolutionary conservation of the observed conformational transitions across ACS homologs. These findings establish a ligand-coupled interdomain rearrangement mechanism underlying catalysis by ACS enzymes and a structural framework for inhibitor development.