  The original ideas of Cooper and Dryden, that allosteric signalling can be
induced between distant binding sites on proteins without any change in mean
structural conformation, has proved to be a remarkably prescient insight into
the rich structure of protein dynamics. It represents an alternative to the
celebrated Monod-Wyman-Changeux mechanism and proposes that modulation of the
amplitude of thermal fluctuations around a mean structure, rather than shifts
in the structure itself, give rise to allostery in ligand binding. In a
complementary approach to experiments on real proteins, here we take a
theoretical route to identify the necessary structural components of this
mechanism. By reviewing and extending an approach that moves from very
coarse-grained to more detailed models, we show that, a fundamental requirement
for a body supporting fluctuation-induced allostery is a strongly inhomogeneous
elastic modulus. This requirement is reflected in many real proteins, where a
good approximation of the elastic structure maps strongly coherent domains onto
rigid blocks connected by more flexible interface regions.
