What is Disorder and dynamics?

An intrinsically disordered region has no stable fold on its own and exists as an ensemble of rapidly interconverting conformations, often folding only when it meets its partner; about a third of human proteins carry a disordered region of more than thirty residues, and they are enriched in signalling and regulation, where a flexible segment can be phosphorylated at many sites, bind several partners in turn, and act as a linker. Folded proteins move too: side chains rotate in picoseconds, loops open in nanoseconds to microseconds, domains hinge in microseconds to milliseconds, and an enzyme’s catalytic cycle is a choreography of such motions rather than a static lock-and-key. A crystal structure is one snapshot of a conformational ensemble; NMR and molecular simulation see the rest. Multivalent disordered proteins and RNAs can also demix from the cytoplasm into liquid droplets — biomolecular condensates such as nucleoli, stress granules and P bodies — that concentrate reactions without a membrane, and whose ageing into solid aggregates is one route to the amyloid diseases.