Scaffolds are ‘active’ regulators of signaling modules

Signaling cascades, in addition to proteins with obvious signaling‐relevant activities (e.g. protein kinases or receptors), also employ dedicated ‘inactive’ proteins whose functions appear to be the organization of the former components into higher order complexes through protein–protein interactions. The core function of signaling adaptors, anchors and scaffolds is the recruitment of proteins into one macromolecular complex. Several recent studies have demonstrated that the recruiter and the recruited molecules mutually influence each other in a scaffolded complex. This yields fundamentally novel properties for the signaling complex as a whole. Because these are not merely additive to the properties of the individual components, scaffolded signaling complexes may behave as functionally distinct modules.