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 image (the fractional occupation of the binding sites) and image (the fraction of molecules in the R state). Cooperativity (measured by the Hill coefficient) has strikingly different properties for image and image. 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 image.