Figure 1.

A simple scheme of allostery depicted as a population shift in the free energy landscape. The allosteric system is represented in conformational space by two structural states: inactive (I) and active (A). G₁ stands for the population of a resting system, which favors the inactive state, and the G₂ represents the population after stimulation by an allosteric event. This population favors the active state. ΔG gives the population difference in terms of free energy difference between the active and the inactive states. In the figure, we can clearly see the population shift, ΔΔG_1→2 = ΔG₂ − ΔG_1, due to allosteric activation. The population shift can be decomposed into two additive contributions: the destabilization of inactive conformation, ΔG_1→2(I), plus the stabilization of active conformation, ΔG_1→2(A). The detailed correspondence of the free energy population shift to the thermodynamic view or the structural view of allostery can be found in recent articles (11, 39). To see this figure in color, go online.