Carver, M. D.; Kyriakakis, P.; Monfort, E.; Barry, R. M.; Leschziner, A. E.; Herzik, M. A.; Wilhelm, J.

The actin fold is present in enzymes ranging from sugar kinases to chaperones. Previous work on the actin fold metabolic enzyme, glucokinase (Glk1p) in S. cerevisiae found it could form filaments in response to its substrates, ATP and glucose (Stoddard et al., 2020). Here, we have identified the product, glucose 6-phosphate (G6P), as a second trigger for Glk1p polymerization in vitro. Furthermore, the addition of ADP to G6P-Glk1p filaments causes filament disassembly, suggesting that polymerization is sensitive to the state of the bound nucleotide and/or the transfer of the gamma phosphate. We have also identified a specific metabolic state, the accumulation of G6P during stationary phase, that triggers Glk1p polymerization in vivo. While the structures of Glk1p filaments in either the ATP/glucose or G6P-bound form are not similar to conventional actin filaments, the sensitivity of assembly to the gamma phosphate of the nucleotide provides a conceptual bridge between the cytoskeleton and metabolic regulation via enzyme polymerization.