A Novel Equation for Cooperativity of the Allosteric State Function()

The MWC (Monod–Wyman–Changeux) allosteric model postulates concerted conformational changes between two states: the intrinsically more stable T state with relatively weak ligand binding and the R state with relatively strong ligand binding. The model distinguishes between [Formula: see text] (the fractional occupation of the binding sites) and [Formula: see text] (the fraction of molecules in the R state). Cooperativity (measured by the Hill coefficient) has strikingly different properties for [Formula: see text] and [Formula: see text]. For the latter, cooperativity depends only on the relative affinities of the two states, not on their relative intrinsic stabilities, as demonstrated here with a simple new equation relating the Hill coefficient to [Formula: see text].