When two macromolecules interact, one or both partners often undergo structural rearrangements to establish a complementary binding interface. Such induced fit interactions (sometimes called adaptive binding) are quite diverse, ranging from fine adjustments of a few atoms to large-scale folding or unfolding reactions to major domain rearrangements. In extreme cases, two entirely unfolded molecules can require the interaction to stabilize their structures, for example in forming protein–protein dimers. The energetic consequences of induced fit binding are similarly diverse; for example, locking a few side chains into particular conformations may have little or no energetic cost whereas remodeling an entire segment of protein secondary structure can substantially reduce the binding constant relative to a rigid molecular interaction. This simplistic view neglects changes in solvation at the binding interface, which can have major entropic effects. Induced fit appears to be a common theme in RNA-protein interactions, and two recent papers in Molecular Cell provide rather striking examples of how the RNA component of the complex can induce structure in a disordered or partially disordered protein. One tantalizing possibility from these papers is that the RNAs may not serve simply as molecular scaffolds for folding but also may influence protein function.
Frankel, A. D., & Smith, C. A. (1998, January 23). Induced folding in RNA-protein recognition: More than a simple molecular handshake. Cell. Cell Press. https://doi.org/10.1016/S0092-8674(00)80908-3