Entropy overcomes chemistry

Disordered segments are prevalent in human proteins. Some disordered segments function as interfaces in protein–protein interactions. Here Zachary Wood and colleagues show that an intrinsically disordered tail attached to the surface of an enzyme can shift its conformational ensemble toward a state with higher affinity for an allosteric inhibitor, purely as a result of the entropic force—that is, as a function of its length, and not its chemical composition. Because such ‘entropic rectifiers’ do not have sequence or structural constraints, they would constitute easily acquired adaptations for fine-tuning the energy landscapes of proteins, which may explain the prevalence of intrinsic disorder in eukaryotic genomes.