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Annonce de Séminaires

WINGREEN Ned (Princeton University (U.S.A))
Lewis-Sigler Institute for Integrative Genomics
Getting together: What can enzyme clustering do for metabolism? 

Mer. 19/04/2017 15:00, Salle Grande Ourse, Bâtiment 13, Etage 1

(Physique théorique des systèmes biologiques)

Metabolism is the set of enzymatic reactions that cells use to generate energy and biomass. Interestingly, recent studies suggest that many metabolic enzymes assemble into large clusters, often in response to environmental conditions. Theoretically, we find that large-scale enzyme clusters, with no internal spatial ordering of enzymes, offer many of the same advantages as direct substrate channeling: accelerating intermediate processing, protecting intermediates from degradation/cross-reactions, and protecting the cell from toxic intermediates. The model predicts the separation and size of coclusters that maximize metabolic efficiency. For direct validation, we study a metabolic branch point in Escherichia coli and experimentally confirm the model predictions. Our studies establish a quantitative framework to understand coclustering-mediated metabolic channeling and its application to both efficiency improvement and metabolic regulation.

WINGREEN Ned (Princeton University (USA))
Protein phase transitions in and out of cells 

Jeu. 20/04/2017 11:00, Salle, Grande Ourse, Bâtiment 13, Etage 1


Biologists have recently come to appreciate that eukaryotic cells are home to a multiplicity of non-membrane bound compartments, many of which form and dissolve as needed for the cell to function. These dynamical “liquid droplets” enable many central cellular functions – from ribosome assembly, to RNA regulation and storage, to signaling and metabolism. While it is clear that these compartments represent a type of separated phase, what controls their formation, how specific biological components are included or excluded, and how these structures influence physiological and biochemical processes remain largely mysterious. I will discuss recent experiments on phase separated droplets both in vitro and in vivo, and will present theoretical results that highlight a novel “magic number” effect relevant to the formation and control of two-component phase separated liquid droplets.

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