Scaffold proteins physically assemble components of a signaling pathway by binding and organizing pathway components into complexes, thus promoting efficient signaling along a particular pathway. In addition, scaffold proteins physically sequester signaling proteins into distinct pools insulating improper communication PMID:22878499.

Structural domains comprising this superfamily share the structure of the Fus3-binding domain of Ste5, the prototypical scaffold protein involved in the coordination of the yeast mating mitogen-activated protein kinase (MAPK) response by binding to all three components of the MAPK cascade (Ste11, Ste7 and Fus3) and serving as a required co-activator of the mating-specific MAPK, Fus3. Fus3 is an intrinsically poor substrate for Ste7 that requires Ste5 as a co-activator as the latter binds Fus3 and promotes its phosphorylation by Ste7 PMID:19303851.