National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
1F32GM144981-01
米国
Human Frontier Science Program (HFSP)
RGP0054
フランス
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
R01GM123159
米国
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
R35GM145238
米国
引用
ジャーナル: bioRxiv / 年: 2025 タイトル: Product-stabilized filamentation by human glutamine synthetase allosterically tunes metabolic activity. 著者: Eric Greene / Richard Muniz / Hiroki Yamamura / Samuel E Hoff / Priyanka Bajaj / D John Lee / Erin M Thompson / Angelika Arada / Gyun Min Lee / Massimiliano Bonomi / Justin M Kollman / James S Fraser / 要旨: To maintain metabolic homeostasis, enzymes must adapt to fluctuating nutrient levels through mechanisms beyond gene expression. Here, we demonstrate that human glutamine synthetase (GS) can ...To maintain metabolic homeostasis, enzymes must adapt to fluctuating nutrient levels through mechanisms beyond gene expression. Here, we demonstrate that human glutamine synthetase (GS) can reversibly polymerize into filaments aided by a composite binding site formed at the filament interface by the product, glutamine. Time-resolved cryo-electron microscopy (cryo-EM) confirms that glutamine binding stabilizes these filaments, which in turn exhibit reduced catalytic specificity for ammonia at physiological concentrations. This inhibition appears induced by a conformational change that remodulates the active site loop ensemble gating substrate entry. Metadynamics ensemble refinement revealed >10 Å conformational range for the active site loop and that the loop is stabilized by transient contacts. This disorder is significant, as we show that the transient contacts which stabilize this loop in a closed conformation are essential for catalysis both and in cells. We propose that GS filament formation constitutes a negative-feedback mechanism, directly linking product concentration to the structural and functional remodeling of the enzyme.