PROJECT SUMMARY Intermediate metabolism must be finely tuned, carefully balanced, and robustly adaptable to changes in environmental conditions. While the individual enzymes that drive most metabolic processes are well understood, only recently has the field come to appreciate the widespread role of metabolic enzyme self- assembly in metabolic organization and control. In particular, we now know that dozens of metabolic enzymes assemble into filamentous structures in vivo and in vitro, and that these filaments act as allosteric effectors to tune enzyme activity. This proposal focuses on self-assembled filaments of metabolic enzymes in glycolysis and nucleotide biosynthesis, processes that extract energy from sugar and generate fundamentally important macromolecular building blocks, respectively. We will use cryo-electron microscopy to determine the structural basis for assembly and regulation, coupled with biochemical, biophysical, and cell biological approaches in an integrative approach to understanding metabolic filament function. This work will provide insight into the specific roles polymerization plays in modulating enzyme function, and illuminate general principles of metabolic control by enzyme filaments.