The two mechanisms of allostery that we consider in this article. The irreducible
assembly unit (a protein dimer in this schematic) interconverts between
assembly-inactive and assembly-active conformations, with equilibrium constant
KA. In both mechanisms, only assembly-active
subunits can combine to form intermediates smaller than a critical nucleus. In
the ‘Induced Fit’ mechanism, both assembly-active and
assembly-inactive subunits can bind to larger intermediates, whereas in the
‘No Induced Fit’ mechanism, only assembly-active subunits can
bind throughout the assembly process.