Biology subjects

Carver, M. D.

Publications and source records attributed to Carver, M. D..

2 recordsLinked to original sources

bioRxiv2026

Glk1p is an actin fold metabolic enzyme whose polymerization is sensitive to nucleotide state

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. SummaryThe yeast glucokinase, Glk1p, is an actin fold enzyme that undergoes regulated polymerization in response to ATP/glucose and glucose 6-phosphate (G6P). Elevated G6P during stationary phase triggers Glk1p filament assembly in vivo consistent with a role in regulating glycolytic flux.

cell biology↗

bioRxiv2024

A Role for Cross-linking Proteins in Actin Filament Network Organization and Force Generation

The high turgor pressure across the plasma membrane of yeasts creates a requirement for substantial force production by actin polymerization and myosin motor activity for clathrin-mediated endocytosis (CME). Endocytic internalization is severely impeded in the absence of fimbrin, an actin filament crosslinking protein called Sac6 in budding yeast. Here, we combine live-cell imaging and mathematical modeling to gain new insights into the role of actin filament crosslinking proteins in force generation. Genetic manipulation showed that CME sites with more crosslinking proteins are more effective at internalization under high load. Simulations of an experimentally constrained, agent- based mathematical model recapitulate the result that endocytic networks with more double-bound fimbrin molecules internalize the plasma membrane against elevated turgor pressure more effectively. Networks with large numbers of crosslinks also have more growing actin filament barbed ends at the plasma membrane, where the addition of new actin monomers contributes to force generation and vesicle internalization. Our results provide a richer understanding of the crucial role played by actin filament crosslinking proteins during actin network force generation, highlighting the contribution of these proteins to the self-organization of the actin filament network and force generation under increased load.

cell biology↗