Book

On the Nature of Allosteric Transitions

by Jacques Monod

Chat with this book

Summary

Jacques Monod's "On the Nature of Allosteric Transitions" presents the central thesis that regulatory enzymes control metabolic pathways through reversible conformational changes induced by binding effectors at sites distinct from the active site. Monod, along with Jeffries Wyman and Jean-Pierre Changeux, formalized this into the concerted (or symmetry) model, proposing that allosteric proteins exist in equilibrium between two states—a tense (T) state with low substrate affinity and a relaxed (R) state with high affinity. The binding of an allosteric effector shifts this equilibrium, enabling cooperative binding and feedback regulation. The book details how this mechanism explains phenomena like the sigmoidal kinetics of hemoglobin and the regulation of bacterial enzyme systems. A reader takes away a foundational understanding of how protein dynamics govern cellular control, with the model providing a quantitative framework for analyzing cooperativity and regulation in biological systems.

Full text isn't indexed yet — this overview draws on general knowledge of the book and its metadata, and chat works the same way.

Key concepts

  • Concerted model (MWC model) — A model proposing that allosteric proteins switch between two symmetrical states (T and R) in a coordinated manner, with all subunits changing conformation simultaneously.
  • Allosteric effector — A molecule that binds to a regulatory site distinct from the active site, stabilizing either the T or R state to modulate enzyme activity.
  • Cooperativity — The phenomenon where binding of one ligand molecule increases (positive cooperativity) or decreases (negative cooperativity) the affinity for subsequent ligand molecules.
  • Sigmoidal kinetics — A characteristic S-shaped curve in reaction velocity versus substrate concentration plots, indicating cooperative binding rather than Michaelis-Menten hyperbolic kinetics.
  • T state (tense state) — The low-affinity, less active conformation of an allosteric protein, often stabilized by inhibitors.
  • R state (relaxed state) — The high-affinity, more active conformation of an allosteric protein, often stabilized by activators.