Large-scale filament formation inhibits the activity of CTP synthetase.
Bottom Line: Structure-guided mutagenesis and mathematical modeling further indicate that coupling activity to polymerization promotes cooperative catalytic regulation.This previously uncharacterized regulatory mechanism is important for cellular function since a mutant that disrupts CtpS polymerization disrupts E. coli growth and metabolic regulation without reducing CTP levels.We propose that regulation by large-scale polymerization enables ultrasensitive control of enzymatic activity while storing an enzyme subpopulation in a conformationally restricted form that is readily activatable.
Affiliation: Department of Molecular Biology, Princeton University, Princeton, United States.Show MeSH
Mentions: To address the reviewer’s concern about the physiological relevance of polymerization mediated enzymatic regulation, we have repeated the CtpS titration experiment shown in Figure 1B with activity buffer supplemented with 150 mM KOAc (within the physiological [K+] range measured in Shabala et al 2009). We find that the overall trends observed in Figure 1B are maintained in the presence of K+; polymerization and a corresponding decrease in enzymatic activity both occur above the threshold value of 1 uM determined for CtpS polymerization (see Author response image 1). Previous CtpS enzymatic activity assays used in the literature typically omit monovalent cations or keep them at low levels, so for consistency with past experiments and internal consistency with other experiments performed in the manuscript, we have not included this data in the main text.Author response image 1.
Affiliation: Department of Molecular Biology, Princeton University, Princeton, United States.