Models of allostery have typically focused on concerted structural changes . For example, the classic induced fit model postulates that ligand binding to one subunit of a protein causes a conformational change in other subunits . The conformational selection model also focuses on structural changes, positing that ligand binding to one subunit stabilizes an alternative (but pre-existing) structure of other subunits . Extensive work establishes there is often a role for conformational selection , though there is clearly a continuum between extreme versions of inducedfit and conformational selection . This conclusion implies allostery can be inferred from proteins' equilibrium fluctuations even in the absence of an allosteric perturbation. Inspired by this implication, numerous methods have been developed to infer allosteric communication from structural fluctuations observed in molecular simulations .